Like Allen suggested there are other things that other people can "invest in" or create and run that might actually add to how desireable it is to come out of the house to your event. I would keep those added things seperate from what you have already achieved. For example it sounds like there might be room for an outdoor trail and this could be another $5 of which you need to harvest 20% or 30% of as a landlord or 50% as an active partner in only that aspect of what is added on.
The $5 bothers me. It says you are catering to the poor people who have no money in your mind. Unfortunately people with no money are by definition not customers. At $5 it says you have no real value and it isn't worth seeing. Maybe all kiddy stuff and unfortunitely the real market where people have money, will travel and carry $100 a month cell phones to call others to join them are ages 25 to 35.
There is nothing wrong with a community event or a family event and someone has to do it but routinely coming up with money from such a thing will never happen. This might be entirely successful and desireable to you as a side deal. The trouble comes in even using the word investment. It is more like the additional people coming in are sponsors of the addtional trail or additional concessions. They may break even or even have those things cost them money and be thought of in the community as a real swell guy. Nothing wrong with that. If you want it to turn a buck is a different mentality, a different customer, a different price point.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.