Just got back from Zaandam today; my kiddo is 8, spent every evening, and part of our 1 sea day, @ Club HAL. He LOVED it.
Sched is 9-11:30a, 1-4p (during the day on sea days) and 7-10 every night. Each session had planned activities--organized games, movie night, going to a show, arts/crafts, drawing, plus there were video games, board games, building toys, etc. One day they made figurines out of some kind of material--I heard that from a brother/sister pair that my son was hanging out with. I also liked that it wasn't ALL day--kids still had meals w/ their families, and you could pop the kids in and out for whatever reason. Kids could stay in Club HAL on port days, but they must be pre-registered--go the night before to sign them up if you're doing an excursion that isn't kid-friendly. I don't know what the schedule is on port days. They don't take kids under 3.
Staff could not have been nicer and I was confident and comfortable knowing he was safe and engaged with other kids on the cruise.
The only other experience I have w/ a kids club is on Carnival and my son was not a fan. I'm not exactly sure why, except that on Carnival they made him wear a nametag and he hates that (he's weird). I also think it was just really crowded--lots and lots of kids on Carnival cruises. No nametags this time around, I guess maybe because there were less kids (we asked; they said that on average there were about 18 or so kids at any given session). There were 160 kids on board (of 1400 passengers), and I imagine that the #s allow for more individualized attention. Also on Carnival, from what I remember, kids could be in there all day--including meals--and that made me sad. I saw the same kids every night having meals w/ the kids club staff, and I just wondered where their families were. I bring my son on these trips to spend time with him. Maybe it's judgy of me, but I love having meals together as a family on vacations like these--that's the time that we can have dessert first, or try new foods together, or just recap the days events over a plate of pasta or the fish of the day. Sure, if I wanted one night to have date-night with my H, or if I was with a big group of people and we wanted to have an adult dinner, great, no problem, but every night w/o your kiddo(s)? That's not for me.
I read before I went that Holland America tends to trend a bit older than say Carnival (avg passenger age), and I do see truth in that, but there were plenty of kids for my son to meet, hang out with, etc. at the pool, in the library/game room/Club HAL. I LOVED the Zaandam (1400 passenger load seems to be a sweet spot for me--the bigger ships just have so.many.people) and will easily and readily sail again.