Assuming I will pick them up?

Urmstongran
If the asker of the favour asks 'Why not...what are you doing then?' my answer would be 'Not a lot but then, that's my choice'.
If you ask a favour there are two answers. YES and NO.
The asker has to be prepared for either response.
I never give reasons as it doesn't alter the answer.

Suggest you organise a trip for yourself and immediate family to Greece asap.
Your sister may have not originally asked you to go for several reasons - maybe she thought that you had other commitments that would make it difficult for you to go ? Maybe she has always got on better or felt more of a connection with the sister she did ask (it happens)?
If you don't want to pick her up from the airport, don't - you only have say that you can't afford to drive all of that way with the cost of the fuel, parking etc (obviously didn't enter her head) and recommend an airport transfer/ taxi company that could do it instead - but why is her husband not picking her up? Or someone connected with your other sister ?

I would not do the pick up. I maybe being petty but if I am not good enough to take on the trip I feel I would not be good enough to be the taxi driver on the way back. Especially in view of the distance.

Is there some compromise re the pick up? After many years of being the extended family's taxi, (few drivers in family including husband ), we now have a decent aircoach service that comes within a mile of our house. It is certainly quicker than time the it would take me to get to airport and return not including hassle/cost of parking and horrid traffic.
Mobile phones make easy job of pick up and buses every 20 minutes.

I have just finished, only this morning, a wonderful book about Crete, Greece and having a connection with the country as you do, i would definitely want to visit. If not with sisters with a partner or friend. These are your roots.
I have visited the town in another country where my mother was born and found it both interesting and emotional.

Re airport pick up ....? Up to you. If it were me I think I might find a good excuse not to. Feels a bit mean though but not unreasonable. It’s a 6 hour round trip! Bon chance.

I don't think I would. If I was not suitable for the trip why would I be suitable as a taxi? Oh and I will a new word come next winter

Urmstongran, I forgot to add that the follow up to, "No, it's not convenient" is "No, it's not convenient". You do not have to justify, explain why you do or do not want to do something or offer excuses. You have the right to say 'no' without being made to feel guilty or obligated. A request was made, was duly considered and has been politely declined. End of conversation. Deep breath, walk away or put down the phone. It's very empowering.

I would pick her up if I wasn't working. I think it would be a kind gesture as you were asked when it turned into a "sisters trip".
I would try to do it with a happy heart and share their discoveries with them on their return.
Of course, as others have said it's a bit cheeky not sorting themselves out but I don't think it's worth a falling out.

Same here, Auntieflo

If she can afford a trip to Greece she can afford a taxi from the airport. I have never asked anyone to pick me up from the airport, it's all part of your travel costs.

Other matters aside, OP, if you've never been, do give Greece a go! I'm sure you'd enjoy it. Dh and I absolutely love it - the Peloponnese (sp?) being a favourite and very beautiful, scenic area. And of course loads of ancient history, if you're at all into that - I know not everybody is.

As some wag put it, 'The Greeks produce more history than they can consume locally,' - or words to that effect.

Slightly off subject, but picking someone up from the airport, would be my idea of a nightmare. Even when I am being driven home, I always wonder how on earth do they know which way to go? Which lane etc? I would need large signposts saying “ This way to ——— Rd”. or somesuch!
So, to answer the OP question, no, I wouldn’t/ couldn’t do it.

You actually said the words "maybe, maybe not"?

Wow! Says a lot.

If you weren't feeling slighted about not being invited, would you do the pick-up?

If yes, do it. If no, don't do it.

Thank you Urmstongran,. Yes that is why I chose the name. The warmth of the sun in winter is the way I feel about this stage of my life. ?

My first reaction would be the same as yours gigi I would feel pissed jarred off.
On reflection though I think it would be better to help out.
Bradfordlass had a good idea about planning your own trip to Greece.

Checked with Urban Dictionary. ‘The sun’s warmth in winter’ for anyone who might not know yet be interested. From the 17th century.

I’ve never come across the word, in a book (I read a lot too) nor spoken. You learn something every day! Well I do ...
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For heavens sake stop sulking and help your sister out by picking her up.

Whilst I agree on one level with mumofmadboys as it keeps the peace with family, I do admire Apricity’s advice. I wish I could be more like that. I’m mostly a people pleaser so I find it hard. I’m going to practice that wonderful phrase ‘no, it’s not convenient’! I love that it doesn’t waffle (or even explain why). Does it actually work? What if the asker of the favour then says ‘oh why not what are you doing then?*. I’d be stuck!! Is there a follow on statement?

By the way Apricity I love the name. Wonder how you chose it? I shall Google the word now ....
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Why not agree to pick her up to keep the peace? It is not worth a major fallout in my opinion.

Θερμούς χαιρετισμούς
You're being very human. I had to laugh when you said you wanted to be invited but wouldn't have gone had you been asked.
My Mom used to say, "But I wanted the satisfaction of refusing!"

And maybe you gave your sisters that impression from the beginning - that you'd refuse - which is why they didn't ask you.

As for picking them up at the airport, possibly you'd have done that gladly if they'd included you in the first place and you'd 'had the satisfaction of refusing'?
Only now, you feel you're being used.

Family shenanagins are always like this - you take the rough with the smooth.

Why don't you plan your own trip to Greece, on a package or with a friend you enjoy? It's your heritage and I'm sure you'd enjoy looking at the family home.

Her trip, her responsibility to sort out her own arrangements for getting to and from her home and the airport. It's just a normal part of travelling. If you don't want to pick her up, don't. It's not necessary to provide an explanation just a simple, "No, it's not convenient." Try to separate the other conflicting emotions about your sisters' planned trip to Greece and the matter of airport transport.