Man, the pignose!!! It is an awesome amp! the rolling stones have recorded with it!
I think your father is right, because you don't need much power to rehearse in your room... If you get a band, then the buy will be worth it, you'll even need a bigger combo, to cut through the drums...
I have bought a big amp when i was your age, and it sucked, bacause I could never turn it up as loud as I wanted to... So, enjoy your little one, and get a band, most parents think it's a waste of time!