If you're wanting to go the natural birth if you go into labour before your scheduled c/s, the only thing I can think of is to try perineum massage. There is also a product called Epi-No which you use from 36 weeks onward. It's like a little balloon that you insert into your vagina and pump up gradually and it is supposed to get everything all ready for the birth to minimise tearing. I've heard really good reviews about it (bought myself one today actually).

As for keeping baby in, that's a hard one. I guess rest up and take it very easy! No lifting or anything like that - very hard to do when you've got other kiddies to think about though.