I believe that MR points transfer at a 3 to 1 ratio to SPG points. Thus, your hard earned 62K MR points would only be 20K SPG points.
W South Beach "costs" 30K SPG points per night. You don't have enough for one night. I found rates of sub-$500 for the date range that you gave. AAA rate is sub-$400. I'd definitely look at what benefits Platinum travel can offer, and consider paying for the hotel. I don't know rates at this hotel, but was very surprised to find the following for $399 AAA, $499 otherwise:
Fantastic suite, non-smoking: King Bed,
Non-smoking,
746-1,129 sq. ft. / 69-105 mē,