I think you are fine. Bisacodyl is not a fast acting laxative. But what if it triggers childbirth? What if you wake up with a baby next to you? (I can't see tickets but I think you are due any day. Otherwise - no early baby jokes intended)
What do the directions on the laxative say? Most take 8 or so hours to work. That, coupled with the fact that unisom barely helps me sleep, and I vote, go for it.