I think you should tell him.
I think you start out, as suggested by MorgnsGrl, by telling him how much you love him, how much he means to you and how you really do think of him as your own father.
Then I would tell him the things about having your first baby in the hospital that made you so uncomfortable that you didn't want to repeat that. Tell him you really had considered a birthing center when you told him that, but that after further consideration you and your husband have decided on a home birth with the delivery being done by a midwife. Reassure him (repeatedly if necessary) that if there is even the tiniest problem, she will transfer you to either the birthing center or the hospital immediately where you and baby will have the best, most modernized care money can buy.
He still may be terribly uncomfortable with it, but if he continues to protest, just say "We've made up our minds about this. We think it's better for me, the new baby and our family to do it the way we plan. We thought about it a long time and considered all the different angles. This wasn't a decision we made lightly. Please try to accept that this is what [husband] and I really want and what we think is safest and most natural for our family."
Then don't discuss it further. Once baby is here safely, he'll be fine. Resist saying "We told you so!"