Thank you etiquette

My granddaughter is only 4 and @keepingquiet she did get lots of gifts. Her mum thinks it’s good to send thank you notes even if my granddaughter only put her and brothers name on some of the notes. Being at school and tired after long days they only did this for an hour or so at the weekend,, stopping when she was getting bored. So that’s why it took a month.
My daughter has now text her cousin apologising for not including him on the thank you note.

Just saying “thank you” for a present, along with “I hope you’re well” can be done by text, WhatsApp, video or phone, or even writing a thank you card, or in person, so long as it’s done I don’t really care how

I agree that a text, call or message is absolutely fine. Making a four year old write letters for six weeks after Christmas seems like overkill to me. Also, is the upset son an adult? If so, getting upset over something like that also seems rather dramatic. The letter was from a young child, for heaven's sake. she's not old enough to deliberately snub him.

It is 100% not the job of a grandmother to remind teenagers to thank other people. I do thank people for gifts, and brought my children up to do the same. When they grew up they were sometimes a bit lax - just typical teenagers with their heads full of other things - and when they left home I didn't even know when or whether they got gifts from other people. My mother used to keep on at me about whether X liked her present or if Y had worn his new shirt yet. I had no idea, as they were miles away. They would always say thank you but usually when they next spoke to her, so it was more a conflict of expectations than rudeness or ingratitude. I'd be even less likely to know if my hypothetical grandchildren got things, and absolutely wouldn't get involved in anything like that. It can take the pleasure out of the whole thing.

I don't know why people get so het up about presents. I was ill around my last birthday, and hadn't spoken to my mum for a couple of weeks, as I was sleeping a lot and generally under the weather. When I was better and spoke to my sister, she said that Mum hadn't called me as she was waiting for me to ring to thank her for my birthday present! As it was, I just had a virus, but she didn't know that - I could have been at death's door and she wasn't going to call me because I had been given a gift and hadn't thanked her. Ironically, she had handed me the gift in person a couple of weeks before my birthday (so she knew I had got it safely) and I thanked her then.

I completely understand wanting to know if a parcel has arrived, so I am careful to let people know if they have sent me something by post, but when I send to others I use registered delivery where you can track it.

I've just looked up Swedish etiquette.
Swedish people are very polite and send thank you notes, letters, texts and WhatsApp messages.
Rather similar to us.

Just send the son a card apologising for missing him out.. It was a simple mistake..

If GD was ‘almost five’, she is doing well to be writing numerous thank you notes, even with mum helping.

You spent weeks writing thank-you notes? How many gifts did you get?

Saying thank-you for a gift when given is a common courtesy- but you can thank people in person, over the phone, by text or e-mail.

This is the method I use and never expect people to do otherwise.

If a gift is ordered on-line I like to be told when the parcel has arrived and do get annoyed when I have to check up on this myself.

No one is pressuring you to buy anymore gifts so it is probably a good thing that you stop sending them.