We are working on the same...trying to schedule time for everyone to get their needs met. P and I have three kids (ages 10, 6, and 3) and S has two kids (ages 8 and 4), so we feel your pain! Luckily, her ex husband takes her kids every weekend. P also works at home and we have roommates who can babysit for us, especially when the kids are already in bed (during the week, that's when we get together...after kids go to bed. It's just easier.
Good luck to you guys! If you come up with something magical, please let us know!