This sounds lame, but we literally have Friday night penciled in as sex night. That means we stay in, get a bottle of wine and take-out, etc. DS is usually asleep by 9:30, so even on the off-chance he were to wake up, we know we have at least an hour.
We shut the bedroom door, put on some music, gate the dog in another room.... you get the gist. We also try to squeeze in at least one another night during the week. And we make a point to cuddle EVERY night for at least a few minutes before bed.
One point - if we're midway through everything, and for some reason DS wakes up (not crying, just awake and moving around), DH doesn't want to keep having sex. He seems weirded out by hearing the baby babble.