We have cruised on several cruise lines, Carnival included. Indeed it is a different "product" than RCCL or Princess or Celebrity, all of which we enjoy. But the Carnival product is a good one, and in my opinion an excellent value. We were on the Imagination not too long ago and were very pleased with Carnival's improvements since our first Carnival cruise 14+ years ago.
Bottom line is, don't second guess your choice. I don't think you will be disappointed and your kids will be thrilled.