To be clear, this is not a fishing pond. I want to build a site that will allow people to utilize adapted kayaks, WaterWheels (think floating wheelchairs), Paddleboards, and other adaptive equipment. I wasn't planning on having a fishing element, but that would be amazing to see or help someone who is blind, reel in a fighting Bass.
I may be off on the lake size. What size do you think would be best for these activities?
Without motorized watercraft, I think you can go for a MUCH smaller pond. Are there any ponds near where you currently live or work that you could examine? If so, stand on the bank and visualize the activities and how many people might be on the water at a time. You can then send me a PM (private message) with the exact location of that pond, and I can calculate the acreage of that pond from the satellite image.
Knowing your target pond size will greatly help focus your search to properties that have all of the OTHER features that you want.
Since it is not going to be a fishing pond, you certainly can look at some older ponds that have gotten shallower with age. Also, if you build a pond on the property, shallower can be significantly cheaper. Finally, a shallower pond will be warmer during the summer, especially a pond at elevation that may have frozen over during the winter.
A shallower pond will be subject to more plant growth. That may be good if it keeps down the algae (worst thing in a swimming pond), but can cause problems if the plants get too thick or abundant. However, for an activities/swimming pond, you may be able to nuke as needed with herbicides.
[My discussion above is aimed at a non-fishing pond. Even if you optimized for your adaptive water activities, you can still have pretty good fishing in a pond that is sub-optimal for fish management. Most of the pond discussion on the forum is focused on optimizing for fish, but many people have other goals or multi-use ponds.]
P.S. Thanks for the elevation clarification. Stub care was a constant duty with my father. I should have been able to figure out the humidity problem on my own. However, I do live in flat land, so we only think in two dimensions! The humidity we experience is completely controlled by the weather, not by us changing locations.