Kitchen worktop maybe? Wooden floor is fine if you have young knees
I don't use the wrist straps either. Ground yourself by touching the case before anything else. Whilst you are building you'll notice you are constantly touching the case grounding yourself as you go.
The antistatic bags are only antistatic on the inside, outside of the bag is a conductor so not the best idea to put stuff ontop of the bag (watch as people say they have never had any problems but again leave stuff in the bag till you need it out).
The underneath of mouse mats is an anti static surface FYI if you are paranoid about a surface to put the mobo on.
Any more questions or if you need assistance with the build on the day you know where to find us