Everyone is bored with the same sex life sometime in life, but when you are married or committed to someone for the whole life it comes to respecting the feelings of others too. If your hubby is asking you to do something that can jeopardize your long term relationship, then you should be real serious on this issue.
Even if you give in you will be facing it more than once the mental truma and the agony and its not simply the end of the road. It will be coming again and again on your path. Let me tell you dear, Life always gives you a weapon in your hand before you enter into a fight. If you are thinking about your kids and there future, are you sure enough that the future of your kids will be secure if you give in? and what will be the mental situation if ever they find out about all this?
Dont know how you are thing because i am not a female, but even being a male i think you should seek help and hold back your stand and not just give in if he needs something he will get it anyways but if you are not comfortable, you have to make a stand for yourself and your kids.
Best of luck.
some decisions are hard to be taken, and you have to take them yourselves but remember friend, many private decisions always influence many of our closemates. So listen to your heart and do what it says.