not an easy situation, but good that you are looking at it with a keen eye.
I think the biggest concern is that if you just let it grow long and turn into scrub, you will potentially have huge rodent problems which may end up destroying your trees. I learned this the hard way.
Another concern is to keep some grass-free edge margin around your plantings, as pasture grass is super competitive and will really rob your more desired plants of soil nutrients.
Simply mowing and leaving it on the ground to rot isnt a terrible idea. Rake up what you can to use as mulch elsewhere.
From
experience, using fencing to carefully graze animals around your trees is super labor intensive and the animals, IMHE, always seem to find a way to eat what you dont want them to.
Goats may be the worst offenders of all in this regard. Pigs too will hapily uproot your small trees and/or snap them off at their base. Geese will strip the bark off of young trees too. All in all, use caution.
The amount of total hay that you might be able to put up from your area seems pretty negligable, more work than it is worth in the era of
tractor powered swathers and bailers. I agree with your neighbors that it wouldnt be economically sensible either to cut it for hay, or graze their animals on it. Even in a few years with lots more planitings, on 1.4 acres you will still likely have a lot of grass growing around your plants, and that grass will need to be dealt with.
I use a flail mower on a walk behind tractor, as this chops up the herbage so that it breaks down nicely on the ground. It is also very powerful so I can let the grass grow fully to maturity before cutting, so there is a maximum amount of
root mass in the soil. A sickle bar mower would leave long pieces that would tend to not self
compost in the same way. Maybe a self-bagging ride-on mower would work, but I think you would have to mow frequently to keep the grass short
enough for the machine to be able to handle it. For larger clearing in grass, you could teather a heiffer or a steer. Ropes dont work out too well with goats and sheep, they seem like professionals at strangling themselves. But the slow mind of the cow works agreeably with teather grazing. I utilize this on larger spots, anything 20x20 feet or larger. But there are still lots of edges and such that I have to mow. So that is the solution that has worked best for me after years of trial and error, lots of stressed and stunted trees, and more rodent damage than I care to remember.
good luck! sounds like a beautiful
project you are working on.