Car dollies are made to work on a concrete floor. Can't tell from your drawing what kind of floor you have. Also can't tell how level your floor is, as most barns don't have a level floor. Be careful pulling on sideways, may collapse a dolly. Build a door, by an rv cover, build a lean-to on the the side of the barn, you may other options you haven't thought of yet. Besides 4 car dollies won't be cheap, plus a wheel for the tongue jack.
Also check the weight rating and overall size of car dollies. May not be able to fit two of them on the tandem axles.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT