I guess I'm lucky, I only get cramps on the first day. My periods are relatively fast too, usually only 3 days. I try to take my daily walk even if it's that TOM.
I get very very tired. I mean, I have fibromyalgia and I'm always tired but this is worse. I can still do a little though. Today I hiked a mile and then did another 3.5 miles on flat surface. I also whined about my cramps. I'm having my first cycle after a miscarriage and these cramps have been going on for a week! I'm sure it'll let up in a couple days though. I may do a walk tomorrow...or I may just clean the house and then rest.
I really don't think there is anything wrong with taking off 2 days out of the month. If you want to do something, I say a gentle walk would be fine. Or maybe a little yoga? I don't know too many people who work out intensly every single day. It's good to let the body rest so if you need to just walk for a couple days that shouldn't be a problem.
It takes a lot of inner strength to put on fitted workout clothes when I feel like a giant blob, but I normally feel better when I get my workouts in during TOM. Just takes a while to get going sometimes.
If I just start my period and I'm in workout mode and the pain,cramps,bloat hasn't set in yet then I go workout. Usually though, I take the first day off.
Just takes a while to get going sometimes. 
