Probably the two females would be best in the 40 gallon enclosure, and the male can chill in the 30 gallon until breeding time when you can introduce him into the females area.

The only thing is you won't know the sexes when they are hatchlings or juvies, only as they age will you be able to tell. Probably best to keep them all separate anyways until you are sure of their male or female parts.