Back when I lived in a place with a similar kind of plum tree, I dehydrated a bunch of plums for snacking through the year. I also tried just about every plum jam/jelly recipe I had. Then, there was plum cake & plum cobbler, too. I always thought I'd try a plum wine one year, but I never did (that recipe will certainly use up plums!). You might also see if a local food pantry would like some.
You might also be able to use a hanging fruit basket to display some items. Also, a bit of messiness draws people in; so, don't worry about being too neat. And, I'll agree with faithin--people are attracted by things that spin, no matter if they spin themselves.
Charkas really aren't so great for spnning bulkier yarns. If you are planning on plying to get sports and worsted weight yarn, you can spin the singles on the charka, but you may not have enough room on the spindle to ply as much yarn as you'd like.
On another note: I spin mostly on spindles, and, with my lighter weight spindles, I can do lace-weight yarn. The light-weight spindles tend to have a good fast spin (equivalent to using a higher speed whorl on the wheel). I prefer to make a 2 ply; so, I'm actually spinning pretty fine for each of the singles. I may predraft, but I definitely loosing/fluff up the roving before spinning.
If you'd like to try spinning with it (and don't know how to spin), check out the links in the FAQs. They include a link to make your own spindle as well as links on how to spin. Otherwise, I agree with felting. The FAQs in the felting board can help you get started.