Hey, that's a pretty ballsy route, and if you do it, I want to read your report.
I've never ridden most of those roads, but I've driven a lot of them. You'll be going through parts of Philadelphia that I would prefer not to go through; the streets are bad, there are trolley tracks (not to mention trolleys), double-parked cars, and a lot of urban blight. Nothing to be afraid of, exactly, but I would find it distinctly unpleasant.
My preference --disregarding the bicycles-- would be head west to Lambertville, then drop down a bit, pass through Coatesville , Parkesburg, Quarryville, and cross the Sesquehanna at Holtwood, then head south. I haven't ridden most of that route either, but again, I've seen a lot of it from the car, and to my mind it would be way nicer than what you're suggesting.
But maybe that's just me... good luck!
Yeah, I know. I actually sent this route to a coworker and he immediately commented on how bad some of the areas are, and showed me the Google StreetView as proof. But, I've ridden through a lot of bad areas around NJ, Camden, Newark and NYC as well as Baltimore itself, and never have been bothered. I'm big at 6', and pretty well built as is my friend. I just avoid eye contact, and pedal like the bike is stolen! We thought about going around Philly like you suggested but we're trying to limit the number of miles and days of riding to 2 so we can have fun along the way.
Lot of the route through Philly goes along bike lanes that I found here:
http://maps.google.com/maps/ms?ie=UT...1&source=embed