My pictures won't show up I guess.

This is what I mean by mound of dirt around the tree.

https://www.houzz.com/photos/tuscarora-crape-myrtle-landscape-dallas-phvw-vp~110844458

Trees shouldn't be watered as frequently as grass so I don't like to have grass immediately around the base of my trees. That said, the roots of a crape Myrtle are unlikely to cause issues with surrounding grass. If you want plants around the tree, they should be planted at the same time, so you don't damage surface roots when the tree becomes more established. Crape Myrtles prefer full so presumably the plants you choose to go around the tree tolerate full sun but could also tolerate some shade. As the tree grows in size, it will cast more shade. David's Viburnum is an option but you will want to choose based on your climate and exposure.

The tree would be happier without grass up to the trunk. Less human/machinery interaction and less risk of water/fertiliser/herbicide damage if those are applied to your grass. But there should not be a 'mound' of soil. The bed should be at grade and should not be heaped up against the trunk. if you like mulch do a mulch bed. Or plant the bed with low stuff.