I do special events and one of my clients actually had a Halloween party exactly as you described years ago. . I had a teenager who was in the back yard doing face painting and running some simple games. I went out there every once in a while to start up different activities also.
The adults were in and out of the house visiting and participating (checking on their children) on and off throughout the party.
One of the funny things was the food situation.. For the adults, I had made a fancy vegetable platter. It included asparagus, artichokes, hearts of palm.. etc.. .. and the kids platter was typical carrots, celery, cucumbers and cherry tomatoes.. with ranch dressing. .Then the adults I had some spicy skewers.. and for the kids, pigs in a blanket.
The kids LOVED the spicy skewers and the hearts of palm, artichokes.. blue cheese dressing, the cheese ball.. .. And I am not kidding the adults devoured the pigs in the blankets.. I ended up making 6 dozen that night and pulling out all sorts of fancy mustard's from the hostesses pantry.
The adults drank very responsibly (this was a work related party) .. There was beer and wine. I had a fruit punch for the kids.
We laughed and laughed at the way the party was great, but how the young kids liked the adult food and the adults went ga ga over old fashioned pigs in a blanket.