Boarding cat with bladder issues, super worried it'll stress him out more! What to do?

We are scheduled to go out of town on Friday for a week and we have 3 cats. The plan was to hire a pet sitter to come by once every other day to check up on them - we also have cameras and one specifically on the litter box in case any issues come up. Yesterday I noticed our 8 year old neutered himi/siamese going in and out of the box multiple times over a period of 15 minutes. I immediately thought he was constipated (he struggles with this often). Nothing was there until the last time where he peed just a little spot. Finally he peed normal this morning. He acts fine and normal otherwise but we took him to the vet today. He's not blocked but could be having a UTI - I am worried he might have FLUTD as he's had some weirdness with his bladder prior. No stones or anything but he's had blood cells in urine with no bacteria.

Waiting to hear back from the vet but I am assuming he'll be sent home with an antibiotic and/or pain medicine. If he's going to need to be medicated twice a day I just don't feel comfortable with someone I already don't know coming in and trying to do that. He's hard to pill and fights us and I already had reservations with having a sitter (normally my mom would do this but she'll be with us out of town).

So I have the idea of boarding him at the vet where our dogs will be - they aren't our main vet but I trust them and we've always had good experiences there. I'm just worried this will stress him out and if he has something like FLUTD I don't want to exacerbate any existing bladder issues. I was hoping I could board him with our other two to reduce stress but they said they would all be separated. So I guess I'm back to just boarding him but I feel so sick about it and it's causing my anxiety to sky rocket. I wouldn't say he's a high stress cat (is great with new people) but he doesn't like the vet and he's never been here before.