Hello jsarah01. I recommend : go to Greece and London. Fly from Philadelphia to Athens, and the morning you arrive at Athens airport fly from Athens to the island Naxos. Naxos is a big island, with variety. The best beaches in Greece are at the island Naxos, south of Naxos town (Hora). Have overnight accommodation at a hotel in Naxos town. One day, ride in a bus from Naxos town to a beach. An other day, stay at Naxos town. An other day, ride in a bus to the interior of the island, and return to Naxos town. An other day rent a car, drive to the north end of the island, and driving back to Naxos go the north coast route (scenic). An other day ride on a ferry boat from Naxos to an other island in the cycladic islands, perhaps Mykonos, be there two nights. Return to Athens. Be at Athens two nights. One whole day in Athens : walk through the National Archaeological museum. Fly from Athens to London. I suggest be at London 4 or 5 nights. That would give you two or three whole days at London, plus a day trip to Windsor castle (palace) via trains. At the Greek islands, Mykonos has the traditional small white buildings, and wind mills.