In my opinion, other lines would have a better children's program for your granddaughter.
I know from experience that NCL has an absolutely wonderful children's program. My granddaughter was about 10 when we brought her on a cruise on NCL. It was absolutely Amazing for her. I have no experience with the other cruise lines since we haven't brought any children when cruising other cruise lines.
On NCL, my granddaughter didn't want to leave the children's program and do things with us!!!!! lol. She's now in her 20s and she still remembers her special cruise with us to Alaska.
Whatever you decide, I'm sure she will always remember spending time with you on a cruise.