Your setup sounds a lot like mine, only a little bigger. I built my garage
extra long (about 30 ft) to handle a workbench etc at one end, and about an
extra 30% wider than a single car garage; storage, paint area above just like
your. Mine just has to hold my current '61 TBird project, not two cars.
Anyhow, I did my layout (bead blaster, parts washer, bearing press, bar stock
bender, etc.) using one of those simple $15 architectual drawing programs on my
PC. Got it at Price Club; don't remember the name but there are lots of them.
Just move stuff around til it fits on the 'puter screen. Only thing I really
learned that the program doesn't tell you is to keep the dirty stuff (blasters,
etc.) from the clean stuff (anywhere near your paint booth). Other than that,
enjoy your new work toy.