Okay... night time "control" is different than day time.
It's perfectly OKAY... at this age, that your son is still not completely "dry" at night.
MANY MANY children do not have complete dryness at night. My daughter just recently made 6 years old... she still has an occasional "accident." It's okay. It's just that sometimes she sleeps so deeply that she does not awake to go pee in the middle of the night... she says she even had a dream once that she WAS on the toilet....then she felt wet. LOL
Just put a waterproof bed pad under him... then if he has an accident, it won't soil the entire bedding. That is what we do. It's no big deal.
My daughter, still wore night time "diapers" until she was about 4-5 years old... it's okay.
The thing is, night time "control" and complete dryness will occur when the child is ready... MANY kids even in Kindergarten still wet the bed at night, and/or wear night-time diapers.... the parents just don't go around saying it to every stranger they meet. But its NORMAL.
YOu don't need to have him perfectly "potty trained" at night, if he is going to Kindergarten. The main thing is he is toilet trained and can do it in school. Your Son IS potty trained.... the night time thing is a different thing.
Don't worry. He is normal, he will be fine, he IS potty trained.
Take care,
Susan