I would turn into Humungousaur to take care of the rock monsters.
From there, I would switch into Echo Echo, and send groups of duplicates into the burning house to rescue my parents (with some also outside still to make sure that not all the copies are at danger).
Then, I would go into Big Chill to put out the fire, then hopefully fly away and transform back, acting as if I had just arrived there.
Upgrade - Useful in most situations to adapt with any surrounding technology (and also my favourite alien)
XLR8 - Speed can come in handy in most problems.
Ripjaws - Mainly for swimming under longer periods of time (especially with the master control unlocked).
Ditto - Multiple minds are better than one.
Heatblast - Could come in handy under certain situations, but ultimately just based off of preference.
Upgrade, XLR8, Echo Echo, Clockwork & Atomix
Number 2 has a lot of my favourite aliens
Upgrade
Goop + Heatblast - Goopblast
Frankenstrike + Wildmutt - Frankenmutt
Gravattack + Brainstorm - Gravastorm
Echo Echo + Big Chill - Echo Chill
Upgrade + Juryrigg - UpRigg
Upgrade
1) Upgrade
2) Heatblast
3) XLR8
4) Diamondhead
5) Big Chill
6) Echo Echo
7) Brainstorm
8) Overflow
9) Feedback
10) Gravattack