Having your craft table in the same room as the children’s playroom will of course create the occasionally spillover from one to the other. I’ve been known to swipe legos to make mold frames, and occasionally my plastic D&D miniatures have been incorporated into action figures, etc.
But recently my two kids asked if I’d run a game of Castles & Crusades with them, and I (perhaps foolishly) agreed. I’ve done it three times now–each time following a pretty formulaic routine. There’s no real “plot,” the two PC’s, both fighters, are trying to find something in a dungeon for a friendly NPC in return for a reward. I don’t bother with stats, just give the kids a target number to hit, and an AC to avoid being hit. Each has 10 hit points. There’s an NPC cleric along to cast cure light wounds as needed. Essentially I’m running a 3D version of DragonFable using miniatures, which is good fun.
As you can see in the photo, I use a pretty simple layout. This is actually an earlier modular dungeon I made a few years ago (the second of three that I have made). I also use a dice-rolling tower to keep the dice under control. Plus it makes a fun racket.