I live in Lee's Summit and feel it is a great place to live and offers all of the things you are looking for.
There are some newer and very nice apartments here as well as nice but older and less expensive too.
As for OBGYN, Associated Women's Clinic is great, they deliver at St. Lukes East in Lee's Summit as well as St. Mary's in Blue Springs (just East of LS). I go to Dr. Robert Chang, but have heard good things about many of the other Dr's there.
I have to second Pediatric Associates for pediatricians. They are very nice, have good hours and can get my kids in right away when I call. Dr. Debra Williams is great and so are the other Drs there.
There are 3 good Catholic Churches in Lee's Summit. We currently belong to Our Lady of the Presentation. They have a great Early Childhood Center for Preschool and gradeschool as well. I live right near St. Margret's which is on the East side of Lee's Summit and have gone there on occasion. It is nice, brand new and is getting their parish established...I would go there but prefer the religious Ed that OLP offers for the kids. Holy Spirit is the other Catholic church and it is on the South side of town. It has just built a new church and they do have some religous education and also have a preschool that is run out of the downstiars. I have heard great things about this church too.
Good luck and when you get in town, be sure to get in touch with Parents As Teachers. It is a state funded program for every child birth-5 years old. It is great for your children and and could even be a place for you to use your early childhood experience if you ever wanted to work some. Good luck!