It's too weak the way it is, you need 2 creatures and your opponent gets to screw you. I'd play Giant Grow before that, and we all know how good is Giant Grow.
I would propose a +3+3 and +1+1 and something else, like trample or can't be blocked by flyers, so the choice is harder.
It's already strictly better than Giant Growth, because you can always just choose one creature. It's "up to two" not "two". And Giant Growth is just fine; there's a reason it's one of very few cards from Alpha that is still in the core set.