Dump the substrate with all the baby crickets into a tub, add some carrots and some dry baby cereal in a corner. Now you have a bunch of free crickets to raise and feed your frog!

Put new cricket-less substrate in your frog tank, and you're done
...I mean, I
guess you could kill all the baby crickets instead, but that seems wasteful to me :P I'm all about saving a dollar here and there when I can.