If you like old school, a 347 is a great engine. You can go SBF 427 if you need the number.
Coyote is a great choice for more modern.
LS is a great engine. However, it will ding the resale value and salability.
Any of those can get you 500hp.

You want safe? That is up to the driver. When you and your son finish the car, do a full season of autocross. That way you will learn how to really drive it hard in a safe environment. That would be an awesome father / son thing to do.