Certified GKH Gardening Expert
You will be faced with two very big problems when attempting to grow grass or any other plants under this tree, unfortunately.
Most grasses cannot grow in the shade that the tree will provide. They will require full sun to perform properly.
Another factor will be the highly acidic soil. This tree will cause the soil around it to be much too acidic to support most grass growth.
Should you choose to make an attempt to grow something under the tree, you will be very limited in what can grow here. Even then, given such strict constraints, your efforts may not be fruitful.
Here are some articles that will help: