You could definetly trade those ponyvilles, g3s, and g1s. The fakie maybe too. The mc Donald's ponies might prove hard to get rid of, but maybe some one will want them!
For the buildings and such, I'd put everything sans the g1s into a lot on ebay or craigslist and use the cash to buy new ponies! Sell it all there, and trade the g1s for two other common g1s or g3s you guys don't have. That's probably your best shot!
Best of luck!