I'm not sure how many times/how much eggs will be laid, but I'm sure it could be alot, seeing as how most frogs lay huge clusters of eggs, the most I've heard of is 20,000 from one Bufo Marinus.
I'm not sure, and hopefully someone will correct me if I'm wrong, but in the event that you had tadpoles, and assuming you did not remove them, would it technically matter, because wouldn't the parents just eat them anyway?
Even still, unless you know you have males & females, you won't have to worry, and even then, the likelihood that they're brothers and sisters is not 100% unless you know for a fact they were laid in the same cluster. But, if all that does happen, I can't say for sure what inbreeding will do to the tadpoles or to them once they become frogs, but amongst most animals, inbreeding is something most creatures try to avoid (I think).
I really can't say indefinitely what the outcome would be, but I'd say take it one step at a time. Hopefully someone with more knowledge of these frogs or with more frog experience can give a better answer.