M.L.
I think a lot of this has to do with the fact that your son hasn't had a regular schedule because of the trip, and then he's been ill. It can be difficult to keep (or get back) equilibrium, and it often shows up at night.
Last Christmas one of my granddaughters went through that sort of thing. She was a little cranky during the day, but then would scream - and eventually throw up - every night. This lasted just a few days, but it seemed longer.
I don't know how old your son is. I do like the monster spray idea, if he's really afraid of something. And you can get a new night light (or check at the hotel to see if they found the other one) if if helps him. Try playing soft music in his room, too. But you may just have to work with it a little while until he gets over this hump. As your boy feels better, gets back on a regular routine, and gets a little more TLC from Mama, he'll sleep better. (So will you.)