A tired stroller becomes a weapon of frustration.  A tired arm suffers silently.  Strollers allow people to vent outward.  No-strollers force parents to carry their own weight.  The lesser of two evils is banned strollers.  No strollers = higher fun quotient throughout the show.

Local organizations comprised of AFOLs might be worth contacting.  Google "Pennsylvania LEGO User Group" or "Pennsylvania LEGO Train Club".

Train clubs are your best bet, but tend to be busy with recurring annual shows.  So it may be difficult to get your event added to their schedule.  LUGs don't "display" as often and are generally more social-focused; but they're worth a try.

If you submit a request to any of these groups, give as much advance notice as possible.  Club members commit to requests based on their availability.  Ample planning time helps.  Be sure to include dates and specific times, location, expected number of attendees, and as many details as possible about logistics and space available for displaying.  Ease of set-up is an important factor (2nd-floor events are more difficult).  Also, members prefer wide latitude to the types of creations they may display.  Requests for specific themed shows can be difficult to fulfill.

Typical shows use standard rectangle folding tables.  Members sit behind the display tables while observers pass in front.  This allows constant oversight of the LEGO creations and gives displayers the chance to chat with passers-by.

AFOLs will be interested in security of their creations.  No one wants to return the next day to find their carefully crafted (and often expensive) models damaged or missing.

The duration of your event and expected number of attendees may influence responses to your request.  Set-ups and tear-downs are time consuming.  AFOLs do not want to spend hours loading their cars for an event lasting only two hours.  It is a very nice touch to offer an honorarium, lunch and/or snacks to the exhibitors.

These clubs generally prefer to join large-area festivals where their works may be viewed by many fans.  How-to workshops benefiting a few dozen are not preferred.  But it never hurts to ask if one or two individual members might be interested in coming to chat with your small group.  There are other organizations in the area that conduct LEGO parties, for a fee.  Google "Pennsylvania LEGO birthday party," for example.

If you think your event fits the above criteria, we encourage you to contact these clubs directly.

We hope this helps to guide you.

PS: You also may try contacting First LEGO League and US First to see if they offer youth programs appropriate for your group.