Road trip from boston to miami!!!

Hi everyone!!! first id like to introduce myself, my name is miguel (but you can call me MIKE) im from argentina, 31 yo, happily married with my wife, marina and with a beautiful son bautista 6 moths ola right now, we are both architects and huge fans of your country. ive been in the us several times, last one for our honeymoon, we made a RT, from SF to yosemite, las vegas, san diego LA and back to SF, then, to maui to relax a little!!! and back to argentina.
after years saveing money we decided to go back to the US, this time to de east coast.

fist i have to tell you that i love driving and im an insane fan of american muscle cars, wich are almost impossible to buy in my country, thats why on our last trip we rented a lovely yellow camaro and i have to say that i could not sleep at nights counting the seconds to get back on the car and drive... i loved it. (one item from the bucket list, DONE!!!)

http://img4.imageshack.us/img4/7602/pb090275.jpg

this time i want to take my wife to NY (i went there alone in 2009) but since i loved that city id like my wife to have the chance to go there to. so since we are up there why not to do some extra miles???

the idea is to fly to BOSTONon november this year or april/may 2014 spend 2 or 3 days there, take a bus or something (i need your help in transportation posibilities) to NYC stay for 5-7 days in manhattan and nearby areas, remember that as architects we will be very entertained, the first days we´ll only enjoy the city but the last days we would like to go a little bit far out from the big apple, so i thought on renting a car!!!!!!!!!! to visit a few places nearby NY and then start going south and the checkpoints would be PHILADELPHIA-WASHINGTON-VIRGINIA-NORTH CAROLINA-ATLANTA-GEORGIA-SAVANNAH-FLORIDA AND MIAMI we know its too much for one trip, but since the economy in my country is a disaster we have to try when we are already there, right?? also some places can be removed, but we´ll see

the total time for the trip would be something about 21 days staying 2-3 days in boston, 5-7 in nyc, 2 in philadelphia, 2 in washington 5 days in miami and the rest in between the other places i mentioned before remember that driving away from this checkpoints for us is not a problem, we love nature, architecture, food and wine, so driving extra is always welcome if it worth it

the things to solve are.

-when/where to rent the car (car rental non negotiable)
-parking cost in mayor cities (should we stay outside but near the big cities?)
-which things are a MUST along this route besides the mayor cities, i mean, what shouldnt we miss???
-lodging, we are not rich people at all, if i were the only one traveling i could sleep in the car, but with my wife and son is not possible, so id like on road nice, safe and not too expensive hotels with free parking spaces like the ones we foreing people see in the movies, of course an exception can be made.

im certainly missing a million things but theres time, so any comment will very much appreciated
please forgive my english writing, im a little bit rusty these days

well be on touch!!!!!!!!!!! thanks for everything!!!!!! best regards, mike!!