leaving cats while traveling

I am going away for 3 weeks, I am concerned for my 2 cats. Will they be ok? My granddaughter is going to give them fresh water and food and clean the litter box every day. I also told her to play and talk to them for awhile.

How old is she? If she's there twice a day and plays with them, etc, they will be fine. I was a catsitter for my neighbor and she was gone a lot, and I went to her house twice a day and every once in a while just stayed and watched like, a half hour of tv and just sat with her cat (it was very sick, so didn't really want to play). I catsat my sister's cats while she was away, but I live about 45 minutes away so I couldn't go twice a day. But I spent the night there a couple times, which the cats loved.

are your cats used to your granddaughter? as long as they are fed, water, litter changed they will be okay