War-games and board games using various different systems. Warhammer, X-Wing, Kill Team, etc. We usually have various boardgames.
We usually have a painting / modelling table as well for those that don't want to play but just pain / model.
Kids own models, but having some of your own for those that don't helps.
Music and snack's also go down well.
Learn various different gaming systems and play them with the kids, you will usually have several kids that already play some style of wargame. A local wargame club might host this?