You are going to struggle to get 3 on all but the most rushed 10s or poor layouts.
I would suggest upgrading your Loons to 6 ASAP as LaLoon/GoLaLoon variants will give you the best chance to 3 star other 10s at the moment with your baby heroes. But note LaLoon can be a high risk 1/3 strategy sometimes. But if you are going for 3 that's probably going to be your best bet.

