How can I get my baby beardie tank hot enough?

Yes heat rocks can burn, but I have used on with no problems for years. I wrapped it in an old sock so the surface can't touch the lizard and the heat still s. However, there is one very important piece of information that you left out and no one else picked up on...what size tank are you setting up? Someone else noted that you didn't put what the temps are right now in the tank. You could add a ceramic heat emitter (no light only heat, use an open dome so it doesn't over heat), put a larger wattage bulb in night cycle. Put a towel over part of the tank, I do this when it gets colder to help keep heat in the tank. I personally wouldn't use Aluminum foil only for the fact that you will restrict air flow and that may cause more problems in the long run. I hope that the tank you are using for the babies is at least a 20 gallon for now and you plan on having a 55-75 for them when the grow up, or two 30-40 gallon tanks in case you will need to separate them.