Here is what I would do, based on my observations of frogs and toads in my care:
1) Feed them a little more than usual before leaving. An extra cricket or two.
2) Make sure the water in the enclosure is clean.
3) Maybe reduce the heat a little. Sometimes if I'm gone for a couple days I'll turn off the main heat lamp. I'm in effect creating a cloudy, cooler stretch of weather. The frogs are still warm enough to digest their food, but their metabolism is down a little so they won't burn off as much. Since the weather in their natural setting is not always 80F during the day and 70F at night (or whatever your settings are), they will do fine with a short, slightly cooler period. NOTE: I'm not saying let it drop into the 50s, for example.
These guys would have to endure far harsher conditions in the wild. A short period without food under while completely free of predation, and having plenty of water, will do them no harm.