A plow, disk, and harrow will do the heavy, medium, and light tillage you need to work up 5-10+ acres of land to a nice finish. Plows work well in long straight rows tho, not so much in small tight spots.
For working around buildings, small spots, around trees, etc. a tiller and landscape (aka York) rake will be much more manuverabe, & perhaps more useful to you in gardening and driveway mainteinence in the future. The tiller will be slower if you are looking at 5+ acres, but this is a onetime job, so no big deal.
End of May and clay - you are past the good time of year to be doing this, perhaps you are looking ahead to August which again is a good time for this job. Plows like to make big chunky lumps out of clay.
I'd lean towards the tiller & landscape rake. Could easily use a harrow instead of the rake; your box blade will come in handy as mentioned for some light root ripping & leveling as well.
--->Paul