It sounds like a decent plan to me. Of course, we would have to know what all the factors are, like; do you get standing water under there, etc.? I would consider a dehumidifier, with the vents closed, unless you have a standing water problem, which would be handled through drains and/or gutters, downspouts and/or exterior grading etc. I might consider using 2" Celotex brand (poly-iso-cyanurate foam sheet) insulation for under your floor. First put another plastic vapor barrier on your joist bottoms and then nail the insulation sheets over it with washer-nails (large plastic washers on the end of nails or screws). good luck, I'm sure others will have other thoughts as well.