Yes! Bring them, if you want! There is a swing set and plenty of room to run wild. The whole place is a play ground. There are also some cribs in the house for naps if needed.
There's plenty at the start of the gravel drive way, there isn't much parking at the top, just a circle for turn arounds, but those who can't walk can be dropped off or picked up.
If your invitation is addressed to both of you, then yes, if not, we would prefer if it was just you.
Tether ball friendly. That's a joke, but really, wear something cute and comfortable that you wouldn't mind playing some pick up games in. Garden Casual.