My advice is to move on as quickly as they do. Deal with whatever problem behaviour there is, but don't hold a grudge and even make s particular effort to engage with that child a little later. There are children I get on better with than others (similar interests or personalities), but I actually make more of an effort with the ones I don't gel with because they're kids and I'm the adult.
Discuss standards expected with the other adults in charge in advance. Agree things like consequences, bedtimes, etc beforehand so you're all doing the same. It sounds like you're a nonteacher so you may need to compromise and follow the teachers lead on some things
Let other adults discipline your own child as much as you can, obviously barring immediate safety issues. Stay in the background as far as your DC is concerned. You're not at home, you're not in sold charge, you might need to let slide things you wouldn't normally, it's ok, they're year6, they'll understand that being on a school trip is a different situation from being at home or on a family holiday
Make it clear that certain things are non negotiable and why (eg safety helmets for certain activities, staying in groups not wandering off on their own). Others can be negotiated eg if they prove they come back when they're supposed to, they get more freedom. If they prove you can't trust them, they get lesd