Welcome to the community and thanks for posting. Sorry to hear you've got no mobile data.
To be honest I find it hard to think they could have done much apart from turning data off. But then again I don't have kids so not sure exactly what mischief they can get up to
You've already confirmed mobile data is turned on and a factory reset should have cleared any settings they may have unknowingly changed.
I appreciate you said everything else was okay but just want to double check. Does the handset show 'Virgin' as the carrier? Can you make/receive calls? If you can't then it's possible the SIM card has been unmounted.
Failing that, you could download the settings again to your handset. All the instructions on how to do this can be found by selecting your handset here.