Donating it for a park isn't as easy as it sounds. Parks require landscaping, maintenance and upkeep. Typically, the town won't have the funds necessary to do this. Unless you include a fat wad of cash, they're unlikely to accept it for that purpose.
An Airstream for an airbnb is going to need utilities. Is the lot improved? It would also require day-to-day attention. It is anything but passive.
Others have nixed the Tesla idea for good reasons.
A farmer's market needs to be managed by someone and there are companies that do this, but you won't make much money on it. You will possibly add to the general ambiance of the area. Same for a community garden, except it's going to need water and porta potties, as previously mentioned.
Have you tried asking the town officials what they might like there? Maybe they've been dying to have an "X" somewhere but don't have the land.
It might be kinda cool to have a library named for your family on that lot. Typically though if you designated the land for a library, it would require a cash donation, just like a park would. Unless they really, really wanted the land for that purpose.
Personally, I'd ask myself how my life would change if I didn't own the property. If the answer is not much, I'd sell i, or donate it for the tax write-off.
The final option is to continue on as you have been, which is paying the taxes and otherwise ignoring it while you go about your real lives.
Interesting question, though. It will be neat to see what you decide, so please keep us posted.