Unfortunately, what you are asking can really only be done on a rooted device and, to my knowledge, Snapchat has root detection which will prevent it from working. There are potentially some 3rd party apps you could use, but those run the risk of deactivating your account

Unfortunately, because most Android phones lack any kind of depth sensing hardware, there really is so good way of doing photogrammetry on an Android device. There are a couple, but they are cloud based. If you are okay with that I could provide some suggestions.

I would say go with an older Apple phone. Their stock parental controls tend to be a bit better than what you can get on Android without modding, and (let’s be real) it will probably be supported for longer. When they get older you can disable the features to their maturity level.