how to have fresh steamed bluecrabs in the late afternoon that I buy live in the morning
I think it's a fine question.  If I were in your position, I'd definitely go for option 2 - I think pre-cooked and re-steamed crab would end up a lot like oversteamed crab: mushy and gross.

As for keeping them alive, when I was a kid we used to go crabbing every weekend. Mom would just keep them in a cardboard box in the kitchen until we were ready to eat them for dinner (much to my dad's dismay).

According to Bluecrab.info:


  Crabs can live for several days out of water as long as they are healthy and are kept cool, moist, and stress-free. The optimal temperature is about 50° F., anything colder will ultimately kill them.


If I remember correctly, mom would keep a damp towel on top of the box.  But that may have been dad not wanting to look at them.