Hi Randy, a brick retaining wall will really look great! Working around a mature tree can be a challenge. I see there is already a bit of ivy and a walk between the two levels. Perhaps you could post a side view to encourage more comments, along with zone and general area. Dimensions would also be helpful. Is there irrigation? Unless you have trouble with runoff or soil washing away, the slope shouldn’t be a problem. You might want stay with low growing ground over on either side of walk.

The length of the wall on the side is about 31 Ft and the little wrap around in the front is about 17ft.

That tree came with the house and to be honest, we're not looking to stay in this house for more than a couple more years, so if possible, I'd like to build the wall around it.

I am trying to get some ideas on how to design the wall with the tiered approach. Would I bring the wall all the way to the front?

Here is a fairly flexible low tech retaining wall method that uses bags of concrete mix. It's usually used for utility applications, but it is strong and does work. But it doesn't look bad if care is used in building. Courses need to be laid with uniformity ... straight or curved, without undulations in their run or rise.

You are never going to be able to excavate close enough to the tree to build a wall -- any wall -- using the same layout as is currently used. You'd need to bring the wall out onto the driveway, possibly saw-cutting and removing a strip of driveway, in order to go around the tree. Rather than stepping course down at the end, the wall should make a 90* or similar turn. At the far end it would tie to the house. At the near end it would die into the grade ... kind of. In the detail below, I'm showing how each course would set back from the one it rests on, which would give the wall a lot of stability. The bottom course would "hook onto" the drive by having the back end of the bag sag into a recessed area that you create next to the drive. The wall is built from concrete bags just as they come from the store, After it's finished, it's kept wet for some hours, by periodic sprinkling, And after it's hardened up, the wet paper is removed. Any that can't be removed from seams can be burned with a torch after the wall has dried. The big flaw in my picture is that I drew bags stacked directly above bags where all the joints line up vertically. You'd actually want to lay the courses in a running bonds configuration. (It would not need to be a perfect running bond ... just so the joints did not line up above one another.)

If it's a DIY project, I might have a suggestion. First I would need to know the climate there and the measured maximum height of the wall (the photos seem to indicate less than 4 ft.

I live in Michigan, so we get the the 4 seasons. The maximum height is about 18 inches.

How about a nice hand stacked cobble stone wall. Esthetically pleasing and perfect for a do-it-yourselfer.
I would say roughly 10 tons of stone.

I don't think what I had in mind would work because of the frost depth. Sorry.

Whatever you do, I would suggest you have a walk with steps across the island near the garage.