We hiked up Galatea Creek to the 3rd lake with both kids (ages 10, 12) and the dog (6 pound pom) no problem. The kids did get tired at the 2nd lake but we managed to coax them all the way to the third.
In my opinion this is a perfect day trip if you go to the third lake but maybe not the best option if you think you can only make it to Lillian Lake (the first one). If you want a good backpacking trip for kids or for an inexperienced party this is a pretty decent option.
The views at the 2nd and 3rd lakes are amazing.