It's wonderful- a nice slow paced family place. We love going there (and my oldest is 11
Couple things that haven't been mentioned. Keep in mind it is in the mountains and in May, esp, it still may be cool. Bring a couple layers, fleece and a windjacket. The park is super small (compared to, say, Disney

) You could easily send someone back to the car for an extra layer if you need it.
On the flip side, there is a little water sprinkle type section. You may want to bring bathing suits for that. (Weather dependant of course whether you want your kids in there that early in the year.)
I believe they still have free strollers (been a while since I was in need of a stroller...) but they' are old/upright ones. I'd bring my own.
Stressing what someone else did- the food is very reasonably priced. We usually bring in some snacks for my DD since she wants to eat 24/7, but I have no problem paying their prices for the meals.