Your last comment made me think of how you could really benefit from reading 'How to make relationships suck?' by Franklin Veaux, to be found on his polyamory-related web page at http://www.xeromag.com/fvpoly.html
. It has a lot of advice on projecting and story-telling and I think it should be mandatory reading for anyone embarking on A relationship, be it poly, mono, whatever.
I'm involved with a couple who have a small baby, too! So we have a lot of sex outside of the family bed, and steal little moments during the day for sex and cuddles. The good thing about having three adults around is that one can always mind the kids. And thank goodness, even children need to sleep sometimes!