Hiya, is Jamie still in a basket or in a cot now? We had an overnighter when Imogen was 3 months and took literally everything with us including mobile, just to keep it all familiar, but imogen was in a Moses basket then (just).
You could try using the travel cot at home for a bit to get him used to it?
Don't be afraid to take absolutely everything you could need including playmate, bumbo, as many toys as you can carry etc. And stick to the routine - bath before bed etc and go somewhere quiet for that last feed so he doesn't get all excited last thing. Don't feel you're being antisocial while you sort him out, especially if it means having the rest of the evening as Grown Up time. (who am I kidding? Imdont have grown up tome now!)
I treated our first weekend away as an experiment in portable survival rather than a holiday so I didn't have any expectations to fail to live up to!
Good luck honey xx