What great glider parents you have! And I believe it would be quite obvious if you have little boy joeys. The poms are hard to miss.
Here is a picture of a male joey, you can easily see his pom
And here is a baby girl, see her pouch? It is right underneath my thumb
Good luck, can't wait to here which gender you have! By the way, these are 2 days oop joeys, so yours are not too young :)