My son returned in August from his overseas travels which started in Israel. He was traveling for 8 months.
Athens is not recommended now. High, high crime rate, targeting of lone travelers, almost no police presence. My son worked in Greece for 3 months (on Kefalonia) and this was the advice the Greeks had for each other and for tourists.
With only 10 days in Israel on Taglit, your son may like to do several more days in Israel. You barely scratch the surface on seeing the sites in Israel with this 10 day tour. Most Taglit tours will concentrate either on the Galilee, which means very little, if any, time in the Negev, or in the Negev, which means almost no time in the Galilee. Having more time in Israel and then adding Petra, Wadi Rum and maybe other sites in Jordan would easily fill 8 days. Desert Eco Tours, menitoned by Shoshi above, does some great standard tours but also amazing physical hiking and adventure tours in and around Petra. I have used them and was very pleased with their services.
Edited: 8:16 am, November 09, 2012