I don't think the point is how many times per week, but rather that your husband and you should both feel satisfied with your sex lives in general. I met a woman who has 3 kids and has been with her husband a long time, and she swears they still do it 4-5 times per week! Great for them! But others only do it once a month, and both partners are happy with that. Personally, my husband has a lower drive than I do, and he always has. I've known that about him from the beginning, and so I don't expect things that aren't going to happen.
We are more tired and distracted now from kids, and for us, it has actually helped to "schedule" the time. I'll just say, "Hey, it's been awhile, how about Saturday?", and it's nice, because then I know for about 95% certainty that something will happen on Saturday and that he won't end up saying he's too tired or not in the mood. Now it could be in the early morning, or while the kids are napping, or after they go to bed... That's the fun is not knowing exactly when, and also looking forward to it for a few days. (Plus then I know when to shave my legs, etc!)
Anyway, the point again is for you and your husband to agree about an "amount" that will satisfy you both, not try to meet some national average. Hope this helps. Good luck!