Yes, this is the kind of post that raises a lot of questions; but I find that many families have unspoken 'expectations' about how members will behave and what they will do.
And yes, Christine, although I haven't camped with twins, we took all of ours camping from about 4 months old, so I have camped with 3 under 5s, and 4 under 7s (both parents present) and have been with my sister when we had 7 children between 2 & 10 with the two of us. We have camped in snow, pouring rain and sun, all over the UK and Europe. And if there was the odd evening that felt cold and damp, the magical places have made up for it. I feel fortunate to have had the experiences that I have, the people we have met, the places we have seen.
I write this, mainly to explain that camping, even with small children, is a positive experience for many - but the difference is that I make no such expectations of anybody else, and certainly don't impose them on my lovely DiLs or SiLs.
Neither am I writing to demonstrate how 'capable' I am - I have (for instance) never flown with any children (that I am responsible for) and quail at the thought of it. However, coping with anything unfamiliar or worrying needs explanation, communication and requests for / offers of help.