I had to go away twice since I've had my Leos. Once for 3 days, once for 2 days. Both times I just put a lot of mealworms in a dish (that they could not escape from). You can also put something in there for the mealworms to eat if you want. Maybe a piece of potato or apple. I'm not sure what is the best to feed them, but definitely something big enough that your Leo won't accidentally eat.
My problem was not the food, but the moist hide drying out. Now I put a folded up paper towel in there and make sure it's fully moist...along with the moist substrate (i also use paper towel for that). But I'm sure if you are using moss or something like that you will be just fine.