I am going to be contrarian. I urge you NOT to go to Greece (1) if you have only one week and (2) it is in March; still the rainy season, and cold and (3) with 3 youngish children.
Why? Cruelly short time, iffy weather. From Annapolis, your SHORTEST trip will require a flight before noon on day 1, changing in Philly, Newark or New York, to arrive by 9 or 10 on day 2... a 15-16 hour duration +7 hours clock-time change = 24 hours. Your family will have only 6 days, then an exhausting trip back... not to mention that rain may interfere with sightseeing (AND many things closed due to Easter) and it's too cold to swim or sunbathe. All this, with 5 round-trips costing at least $800 each!! Unless you are totally wealthy, I URGE you to save Greece plans until you can go for 2 weeks -- go in Mid-June, see Athens, & then enjoy beach time in perfect weather on a perfect island for young families, such as Naxos.
If you want Europe in March, do London! Short flight, much cheaper, loads to do indoors if weather is bad, a good intro to foreign travel. "Old hands" can enjoy Greece at any time, but I beg you, don't have your first Europe trip be a rushed visit in a rainy Season that might mar your impression of Greece - a magical land that is meant to be seen in warm sunshine.