Congratulations on your second child coming soon. It may be a little rough at first but once everything settles down I'm sure you'll be able to still find some time - even if you have to work out at home.
If not, you can go to the gym more when they are bigger. At least my oldest watches the others while I go to the gym now - finally...
I hope you can get some type of Daddy (Parental) Leave or holidays from work (unless Mommy is going to of course).
Good luck,
OD