I haven't read through the responses so I'm not sure if this is repeat advice or not. As you know I have a 6 year old and there have been MANY times I've been in your predicament. Your girl is using the kid as an excuse not to give the vag. There is no reason not to have the seckuals when the kid is in the next room, with the door closed to boot! I've knocked it out while my daughter was in the same room awake. It's easy, spoon from behind with a blanket over you and slip it in, just can't get too worked up and start pounding for obvious reasons(*disclaimer: you do need to be at least 7" for this move to be beneficial).
I tend to run into this quite often while we are on vacation with the little one. The shower is another great spot bc u can lock the bathroom door and play it off, plus water dampens the moans and squeals of passion. YWIA