Your child is not bed wetter; just not fully potty trained yet. And at night only, at 3yo, I’d say that is pretty normal.
I have to agree that maybe you should skip the pull up. DS2 is a camel; he doesn’t pee a lot, but when he does, I swear it’s a gallon—pull ups couldn’t hold it. I'd go with a regular diaper. Doesn't Pampers make a diaper that is an actual diaper but for quick changes it can go up like a pull up?
DS#1 had his only accident at night from 11 months at WDW. He was just so sound asleep, he didn’t wake. Not a problem at home, but WDW is a different beast. Housekeeping was wonderful about it. We were so apologetic, but they kept saying it happens every single night and it doesn’t matter. They only asked if we wanted immediate service or service when they normally provided it (since we discovered it in the morning). They came with special cleaning supplies geared for urine, all new bedding (sheets, bread spread, etc), flipped the mattress, and asked if we wanted a plastic sheet.
If you're nervous about it, bring your own sheet or an absorbent pad. If you bring your own sheet, let housekeeping know so they don't accidentally take it.