I have only built one garage in my time, but I have to agree with Ed that a broom finished floor would be my choice. That is how the floor in my garage was finished. It can still be sealed, but it leaves enough texture on the floor as to not be slippery when wet.
As for the floor drain, I was in the same place with the alley out back. I wasn't allowed to put a drain in anywhere unless I actually connected it with the sewer drain in the house, so I had then put a slight slope toward each door. That way any water will not be standing, but will drain toward the doors and eventually outside.
As was already mentioned, nice looking garage. Congratulations!