K.M.
What a darling name for a hamster!!! I agree with the other posts, he's getting up there in age, but I would also check to be sure he's not too cold. Also sounds like he could use a reduction of food - maybe scale back on the amount of treats he gets and make sure he is eating lots of veggies. Our hamsters loved baby carrots (remove what they don't finish by the end of the day) and iceberg lettuce was a huge hit.
I hope Cheese Nip is around for at least another year or so, make sure you have lots of pictures to remember him by, and I would start to gently prepare your daughter using simple phrases like "hamster live about 2 to 3 years" and leave it at that for now.
Good luck and I'm so glad that your hamster is in such a loving home - they are cute little critter, aren't they?!