Very bad idea--if you are lucky, you'll only get a ticket from the police. It could start a gras or worse, a forest fire, injure someone, fail to release and burn up your plane, or if you are really lucky---"You'll shoot your eye out"!!!!!.
Seriously it's not a really safe idea!!!!It is also prohibited by many local and state laws!
He lives in CA. In 90% of the state you can drive 30 mins and be in the desert where you can freely shoot any gun you want so im sure you can lite a couple toy rockets off. You guys act like he is going to go to the redwood forest and try this.
If the wing tip launches prove to be to unstable do a single rocket right under the fuselage. 1 is better than none.
Good luck.