We have done Carnival and Royal Caribbean with our kids. Will be doing MSC YC with daughter in June. Never have done Celebrity with the kids but wish I had. Here's why I would rather take kids on Celebrity.
1. Better and longer itineraries
2. No theme park in ship
3. Less catering to families and more so to travelers.
4. Less obsession with CocoCay for almost every itinerary from the east coast. I can't stand this place.
My 5 kids have traveled with us for years going all over the US and Caribbean. They liked the cruise ship activities but they always loved the ports where we did "cool" things with the rental cars, boat rentals...etc... They never liked day passes at hotels for some reason. They were all pretty active and outgoing and had no problems with what we scheduled. I have showed them our pictures of the big Oasis class plus videos of Icon and asked would you guys have liked this? My one son said honestly he never remembered what the ship had when he was young, just the islands we went to. We have been on the smaller ships (carnival fantasy) which had I think 1 water slide, and on a sea day they just kept going down all day on the one slide. That's all they needed. They went to the kids clubs and had fun.
I read a lot of parents posting on this site and others worried that their kids may not enjoy this ship or others because of activities. Honestly, being the parent of 5, you don't have to think the ship is Disney and you have to do this and that and be stressed because there's no laser tag or zip line. If the kids were with us instead of kid's club, we just said where do you guys want to hang out and do?, and that's what we did. If they liked the buffet for dinner one night, we went there. If they wanted to play mini golf for hours, we did that.