If you don't neuter him, there is a good chance your colony size will QUICKLY get out of control. If you believe the female is pregnant now, why not go ahead and neuter him so that he is healed and ready for his fatherly duties when the babies come. Then you'll still have a colony, but you won't have to worry about him trying to mate with his daughters when they're old enough. However, you will need to also neuter any male joeys you have so they don't try to mate with Mom or any sisters.