It's been a couple of years since I sailed with MSC, and then it was on the Poesia, but I suspect the programs are similar. We had our 7-year-old grandson and 5-year-old granddaughter along.
MSC is very definitely a European line. The kids liked their activities program very much, except for the fact that the "kids' pool" was a 3-inch deep splash pond. What surprised me about it, since I only knew about HAL's program at the time, was that on MSC the childrens' programs never started before 11 a.m.; on some days, as late as 3 p.m. On the other hand they would happily keep your kids until midnight, including escorting them to the buffet for supper. There was also at least one overnight "pajama party".