The above 2 seem to be the most popular. Are there any other cruiselines that are good for 10 and 12 year olds?
To be honest, in terms of kids' clubs, Royal wasn't great for our 12-year-old. They put them in a group with ages 12-17, which is way too large a range. Within the first day, parents were posting in the Facebook group about rude things the older kids were doing/saying to the younger kids, and when I mentioned it to a staffer, she had no idea. Plus they did things like send them out to play hide and seek on the deck, which I thought was very weird. Someone did tell us that on other RCI ships, the twelve-year-olds aren't in the teen club.
It was an older boat so there weren't the varied entertainment options you'll find on the new ones, but my advice would be to specifically check the structure and offerings of the kids' programs on whatever ship/line you're considering. My daughter would have really liked an 11-13 age group, or something similar (honestly, even just a meet and greet for tweens would have made a huge difference). Instead she hung with us all week.