Just my opinion, for what its worth. First, approach the widow and try to find out if you could pay her for use of the field. Second, even a 2nd hand garden tractor and roller should take care of most of the field. I use a water filled roller, it weighs about 700 lbs mostly full, (you want to drain it before winter), and try to roll every time I cut after it rains. It makes the field very flat for me. This is primarily the stuff I do at my field, which is reclaimed pasture. If you can get some friends together to help you, this should be a piece of cake, it only takes me about 25 min. , 2 or 3 times a week to keep my field cut. The main runway is about 220' x 50'. I cut at 2" so I can fly my 40 size planes with no difficulty. To me, it would be a shame to lose the field that you already have established. So, it needs to be cut by someone with a brush hog once to get the overgrowth down. Then follow up with two or three cuttings with a finish cut mower to get it back to the proper depth again.