Comment Details

Zombie fest as a charity event theme.( inclusive of all age ranges)
Downtown has been presented as a place to draw college and after that age crowd and should try to stick to that (Elm Park is better geared to little kiddies because of playground. 
Event should be geared to promoting it bigger and better so that it becomes a destination
Example of 5th annual Zombie charity event drawing thousands in Fort Myers

http://zombicon.com/about/
http://zombicon.com/event-details/

Event can be all inclusive by putting a pet parade and little kiddie parade at beginning of event

Pets are now most popular “with empty-nesters, single professionals, and couples who delay having children. What unites these disparate demographic groups is a tendency to have time and resources to spare.(Also my only kid is my pet and there are a lot like us) and this would draw me down,pay money to put my darling in a parade,spend more money at a food truck and drop pet off and go back down for other things.
Example 
Copy of example of a 4th annual Boston and a 24th annual NYHalloween pet parade - there are many other examples on the web about pet parades getting very popular and drawing participation and money for causes 

http://www.esplanadeassociation.org/events-2/past-events-2/canine-promenade/
http://www.refinery29.com/2014/10/76848/nyc-halloween-dog-parade-pictures-2014#slide

After theme is decided (and time is of the essence) another whole topic could be open to get ideas. (It would really get the theatrical ,creative resources going )