Mulching around new fruit trees

A friend has cleared a large area to plant 9 container grown fruit trees, mostly apple, peaches and pears.
We found a good sized pile of fine sand, possibly sand used for mixing with mortar years ago. Would a 2 inch layer for about a foot radius around each work until the trees are established? He plans to have grass under the trees and keep it mowed.
It's a big project, he already has a dozed fruit and hates to trim around the base.

I don't really understand what it is you are trying to do. There is a tendency to plant trees too deep. When planting trees, you want a hole that is wide rather than deep with the top of the root ball at-or-slightly-above grade. The top of the highest root near the trunk should be only 1-2" below the surface. The graft should be above grade and turned so it is protected from winter sun. Sand is like any mulch - you need to check what is going on underneath it now and then - the surface could appear dry when the planting hole is actually too wet. Sand will not stop the grass from spreading under the tree - but it will make it easier to yank out near the trunk. You should not be mowing or weed-whacking near the trunk - the risk of damage to the trunk is too great. Make sure your sand isn't salty - I am not sure how to do that, maybe have it tested?

Thanks, Pollengarden. This was my idea trying to put the pile of sand to use, it's in the middle of the new orchard, 6 inches deep and 8 feet wide.
We made substantial progress today, the sand has mostly been moved or incorporated. We laid out the where each tree will go and none are near the sand leftovers. So my question is now mute.
I didn't know about protecting the graft from winter sun. These trees should have been planted last spring, they were a surprise gift, some valued at $50.
Four of us have labored with chain saws and pick axes to open up this space that hasn't been touched in 25 years.
Side question; what is a good pollinator for Bell of Georgia peach? Does it need one?

Belle of Georgia peach??? How you going to grow that in MA??? I believe those are self fertile but two of them would be a good idea.
As far as mulch I don't put any near the base of the tree, mulch can cause all sorts of trouble. Also you really don't want grass growing right up to the base of a fruit tree. The grass gets first shot at the water and fertilizer, when the trees are old it doesn't matter and grass will probably be shaded out any ways.

We have a small fruit orchard (~30 trees) here in zone 5 that we planted 3 years ago. We apply fertilizer and hemlock bark mulch in a circle out to the drip line 2x a year. It's easier to pull the grass out and we can mow over the edge of the bark. Every fall, I put white plastic tree wraps (purchased at a local nursery) around the trunks (the trees are still small), to prevent snow scald and more importantly to protect from bucks rubbing on them - that can do a lot of damage.

Core, he has three Bell of Georgia peach, three apples and 3 pears. They all came from a local supplier so they should be ok in our zone. He intends to mulch them with shredded leaves for the winter & clean it up in spring. It's too late in the season to put down grass seed and it wont get within 2 feet of the trees next spring. He needs something to control erosion.
Rose, hemlock sounds good after the spring cleaning. Thanks for mentioning tree wrap. He also takes in feral cats and they love young trees. He protects his other fruit with an ingenious loose wire fence wrap.
This has been a big project because someone gave him 9 trees he never asked for. The giver expected them to go in my buddy's field but he likes his empty field. So they are going on the edge along our mutual property line.
The pic shows a portion of what had to be cleared. Knot weed, sumac, linden and wild cherry trees along with some nasty thorny vines. The field would have been SO much easier, lol.

That looks like no fun to clear. We have more problems with fungus where I am and mulch just invites that but you don't have worry about that over the winter. Good luck you really can go wrong with free.

Fungus is not too bad here although neither he or I have had nectarines in 3 years. They turn black and fall off, we keep the area clean and use dormant oil, Bt and wide spectrum pesticides. The Winter moths devastated his plums this year, my grapes were victims of a wet spring. Pears did great, go figure.