I think 5 of you will be very cramped in a studio for a week. By the time you pull out the pull-out couch, you'll be climbing over things to get to the different parts of the room. There's only a kitchenette and no washer and dryer in the studio. The resort is fantastic for kids, but if you don't plan to swim and you don't need to be at this particular location, I would choose a nice 2br elsewhere for the space. If you can at least get a 1br at Harbour Lake, that would make a huge difference. I love Harbour Lake, but their best amenity are their pools.
Have you looked at the II "getaways" ? Sometimes their prices are only a little bit more than an exchange fee and you can save your week. Also at this time, if you're looking for feb/mar, you can probably score a 2br at any of the other Marriott's(maybe even Harbour lake) or Vistana Villages, which are all nice.
I don't really know anything about the 2 resorts you mentioned.
Good luck!