They are hard to sex until they are fully grown adults. Then females have a white gland under their arm pit that is quite easy to see.
But I still don't think I would worry about tadpoles as I think they are kinda difficult to breed. You need exact tank conditions.

Once upon a time I had 5 of them and 3 were females I'm pretty sure. I never ever had tadpoles.

Congrats on your new frog. I love them they are adorable....