I’m in Geneva right now (not a holiday, sadly, but feels a bit like one - although that means we’re not earning enough money!).
My midwife said that I should use flight socks (try Wilkinson’s, if you have one nearby - mine seem fine so far), and keep moving on the flight. She also said to make sure I stay well—hydrated while flying.
She suggested I should stick to bottled water, which I most certainly have not been doing! (I think the tap water here is Evian...) I’ve found that I’ve had to be careful with a lot of the local food choices, too - I’ve eaten gravadlax, which I’d probably have avoided given free choice, and the burger I was served yesterday, which DH ended up finishing, was a bit rare. Also, with uncooked cured meats and any kind of soft cheese or salad, it might be wise to exercise caution. (I am SO done with watching what I eat to this extent, especially as I seem to be failing anyway.)
You should take your maternity notes with you, too. I’m carrying mine everywhere, as I’m reliant on public transport and other people to get places, and can’t just pop back to base to pick them up if anything goes wrong.
As you get to 24 weeks, you need to make sure you have insurance which also covers the baby - Ravenhall is recommended a lot on here. This isn’t relevant to this trip for you, but you should check what your travel insurance company says about traveling while pregnant - you might need to inform them.
Good luck - enjoy your trip!