I don't think the Vita is for jumping curbs. It's not fragile, but it's not a mountain bike.
I would get him a hybrid, with skinny tires. That should suffice until he has grown a little more. And you don't have to be so perfect with the fitting, as with a road bike.
2015 Trek Silque SSL
Specialized Oura
2011 Guru Praemio
Specialized Oura
2017 Specialized Ariel Sport