Juju, this is an issue that can be tricky. Your H would have the right to take him to the church of his choice in most places, but if he doesn't even go himself, he can't claim it's his initiative. MIL has no right to do it.
I would be uncomfortable with my child being taken to a church where I didn't like what they preached. On the other hand, you may want to check what they do during the Sunday school, it can be very different from the actual church.
I'm not so surprised at the hypocrisy... I've seen too much of it.
M 16 yrs, WH62, P54 3 adult blended kids EA 11/13, BD1 6/14 PA fall 14, BD2 2/15 Piecing 2015, BD3 12/15 Separated 4/16 WH moved OW in 5/16 Divorced 6/15/17