Here's one I've never seen before and I don't even know how to go about this.

My 7 year old loves planes and rather than having a birthday party, would like to take a short flight somewhere - anywhere - just for the ride. Since we probably wouldn't even leave the airport before coming home, where we go doesn't matter. Our dates are fixed to a Saturday in October due to his school schedule. While departing from PHL would be ideal since we live in DE, UA only goes to DEN, SFO, ORD, and IAH directly from PHL. I was thinking if we headed up to EWR, we would have a better selection of non-business routes that have lower fares. Since the destination is not important, we will be focusing on price. Our requirements are:

1. Mainline aircraft.
2. E+ ( obviously this means no BE ).
3. Can hopefully turn around in the same day, but am not against an overnight if we can get out before noon on the Sunday).
4. I am an explorer card member, so we can check a bag for overnight if need-be, but would prefer to just have a carry-on.
5. Flight not too long (nothing longer than say EWR-IAH). It's all about the take-off and landing. A 7 year old and 3 year old (his brother) won't care about being at 30,000 feet for long).

Would anyone know how to find a route with low fares for this trip? Of course, I can always use brute force ( one city at a time ) but I'm trying to avoid that.