We have seen Gabbit Tadpoles here...
If you look at the things around Munch they are actually Gabbit Tadpoles... their heads resemble that of a Gabbit. I have a poster of this image, and they can be seen very clearly on that (they are difficult to see on this image).
Also the fact that Gabbiar eggs are actually only in a small can, would indicate that Gabbits do actually "grow up".
Mudokons however do seem to be a different story. There has not been any evidence of any child Mudokons in the past... that's not to say it is a possibility.
Abe Babe...