chinchillas are NOT nocturnal.They are crepuscular which means they are more active at dawn and dusk but that does not mean that they are not active during the day.Many people who come to visit mine are surprised by how active they are during the day.
As long as you have done your research and know their needs then they make very good pets even for children as long as they have an adult overlooking to make sure they have everything they need.
Hamsters are lovely pets but sleep much longer than chins and do get very grumpy if woken early.