I think that Graceland is worth seeing even if you're not an Elvis fan, but that's just me! If you do decide to go, stay out of the surrounding neighborhoods. Other stuff:
Wonders Series at the Pyramid (downtown). It's the Art of the Motorcycle this year--numerous bikes both old and new.
National Ornamental Metal Museum--forging at it's finest with all kinds of artistic iron works.
Pink Palace Museum including the Imax.
Beale Street and surounding downtown areas..........up until about 10:00 p.m. After 10, like any urban area, the environment is liable to change on you (locals start coming out).
Our baseball farm team The Redbirds also plays downtown, but not sure what the schedule is like.
There are a few places that sell knives, but nothing special that I've found.
Cordova has numerous restaurants too (suburbs of Memphis out east).
Most of the above events have websites and Memphis has one too. Just be mindful that although it may not seem like when you drive around town, this is a major city and you have to use the same safety precautions that you use in any other. Common sense will go a long way and be careful where you park. A car without an alarm is an easy target. Stay out of the project areas downtown.