Thank the lord for video games is what I say.
Yes it can be a pain in the backside having kids, I have one and my mother lives with us as well. But, remember the thrill of sneaking around as a teenager? use it to your advantage and incorporate it, Dad is just going to the supermarket he exits front door, returns through back door, I am off for a bath will you be ok for an hour? and rendevous sorted........
Restrict your childrens viewing of tv and video games..... it guaruntees that they will be glued to it for quite a while when you do let them at it.
lots of private language, looks and code, communicating what is really going on....behind their back.
My sister lives close so we do a swap once a month we get her kids for a sleepover and once a month she has mine ( apparently we like going to the movies) so at least one night a month nobody can hear what we are up to.
It can be a pain but it can add to the excitement and suspense as well.
Good Luck