Have been to Ethiopia 20 years ago. To this day probably the weirdest country I have been too (40+ in total in case you ask).
1.Try injera the pancake like dish but not expect pancake like taste.
2. If you have any chance, visit Lalibela, on of the most interesting things I have seen made by mankind. Churches carved out of rock. Not one but a good dozen.
3. Semien National Park is cool too but you might not have the time for that.
I am glad you are going.