Sex in marriage is a gift from God. Amazing and wonderful
Sex can be a big part of the glue which hold marriages together. Happily married humans look forward to it every few days (or every few hours as newlyweds), unlike animals who do it only seasonally.
We are one of the few living things who get to do it face to face. We can try it in other positions, but face to face is the one we always come back to! Very simple to use a condom (or other sane method) if you don't want children to result. Or skip it if you do.
Once your Mrs. is past the child bearing years, you can pretend to be newlyweds again . . . if you have the energy. It is as good an exercise as walking and a lot more fun!