We only had a short time there but loved it. Beale Street is fantastic if you are music lovers. A must do is a visit to the Civil Rights Museum. Make sure you give yourself plenty of time there- would say a good 3 hours.
Graceland is brilliant and not exactly as I had imagined. I wrote a trip report when we got back from our holiday last October. Most of it is about New Orleans but I hope you find the Memphis bit interesting!
http://www.holidaytruths.co.uk/viewtopic.php?t=14903&highlight=

Seeings how you're on foot, the best way to see anywhere IMHO, you can walk to Sun Records.

Sun records is where Elvis, Jerry Lee Lewis (Brit tabloids are familiar with "the killer"), and Johnny Cash got their recording start.

Sun records is now visitor friendy, and has become a museum (if that's a fair word to use).
Beale St was were everyone was dancing in a style that is generally believed Elvis picked upon to later become "Elvis the Pelvis'.

Several old style eating establishments/ ice cream/bakeries ect that are still old south. Fried bananna sandwiches (Elvis favorite), fried Peanut butter and jelly sandwitches can be easily found too.

Everyone is in slow motion.

If you visit any Civil war sites, the guides tell the tale from a Southern Point of view. "The War of Northern Aggression" as they put it.

All great to see.
You've planned a teriffic trip, have fun.

It may be a bit late but I'll reply anyway. My girlfriend is a huge Elvis fan and we have stayed at the Heartbreak Hotel twice. Just to be warned the hotel may not be what you are expecting. It is more like a motel than hotel, the big bonus is the 24 hour elvis movies. If you are staying 7 nights you should hire a car, the cheapest way I've found is through http://www.airline-network.co.uk. The heartbreak is in not in a nice area on Memphis, you wouldn't want to walk around much of Memphis at night. If you hire a car why not drive out to Tupelo, where Elvis was born or to Tunica in Mississippi where there are lots of resort casinos. We are getting married in Graceland this year but will only be spending the wedding night in the Heartbreak in a themed suite, the rest of the time we will be staying in a Doubletree. If you need any more help let me know.

Well I am back and have to say...I was so disappointed with Memphis and the Heartbreak Hotel...But Graceland made up for all of memphises short comings

Oh, thats a shame! Have to say when we saw where the Heartbreak was I was glad we stayed near Beale Street. I absolutely loved the music there. Any positives apart from Graceland?