The load on your driveway is a vertical compression, the load is not transferred to the wall. All the wall does is keep the retained soil or material from spreading. A 3' retaining wall is generally considered the maximum before engineering is required. If you build a wall on a solid footing, and backfill material against the wall with gravel (for drainage), then you will minimize the outward pressure on the wall. It should be ok. Be sure to provide for drainage around or under your footing. For even more rigid construction insert rebar through the block and fill with concrete to prevent horizontal displacement. Use rebar or wire mesh every 3rd course to prevent vertical displacement.