Sure, you could plant the trees there. I would plan on keeping them heavily pruned to the shape that best screens the neighbors while still fitting next to the wall, all while not letting them get too high. I would also plan on the pavers raising up eventually though keeping the tree size controlled to about 7 feet should jeep the roots on the smaller side. Were you set on the 2 varieties? Adding 4 different varieties can give you great tasting fruit for a longer portion of the avocado season. A fuerte would be good in there. The branches have a spreading habit so pruning would be a necessity.

They have semidwarf avos now. I bought two at HD a couple years ago.