Spice it up?

I am dating an amazing guy. He may not be my son's birth father but he does think of my son as a buddy. My SO and I get along well and each family likes him and I. They all sense our happiness. My SO works and I mean works A LOT. We do go out on dates (most of which we bring my son along to and we are ok with the fact I spend 99% of my time with him.) We do make time for ourselves and when my son is either sleeping or with his birth father (not man enough to say dad) we do make time for alone time fun. Buttt I was just wondering if any mamas knew any way to spice up the fun for when SO is around? Doesn't have to be just sex either though.