I'm debating trying swapping kids for the weekend with a friend - him and his partner would take all four kids one weekend, and we'd have all four another.
Our kids are 3 and 6, their two are 4 and nearly-3. They do all get along reasonably well, and we know each other's kids pretty well.
I think I might suggest a 24-hour swap first, each way, as a trial, before we do a full weekend, particularly as either couple might want to go away for the weekend. We do live close to each other.
Has anyone done this? What problems did you run into?