Personally, I don't really think places like dog parks and doggie daycare are great places for improving dog socialization. It's a great additional source of socialization and good for dogs who have always gotten along well (or at least tolerated) other dogs. But for one with an already established behavioral problem, it's sort of equivalent to dropping off a child at Chuck E. Cheese who has never been around lots of other children at once before, or who is maybe shy and insecure, and fearful.
I am not trying to make you feel worse, as I am sure he will be fine
Maybe it will work for him... but in most cases, going slower is better. But maybe this daycare has a lot more structure and rules, etc. I'll use the comparision again that usually a parent would bring a fearful child to a more laid back, maybe less chaotic, more rules, structure, quiet time, over dropping them off at a place like Chuck E. Cheese where the kids are just run loose. I would first suggest a training class where you can work slowly, one-on-one, and work on improving his dog manners and then build up to dog parks and doggy daycare.
But the good news is it sounds like he behaved himself!!
That's awesome! If he was showing no aggression, then it's probably mostly leash reactivity that needs to be worked on and not true dog aggression.