Check out is at 11:00 a.m. While you can request a late check out, you cannot do that until the check out day (I've requested and received late check outs the night before at deluxe resorts, but have had no luck at value or moderate resorts except on the day of). Typically, if granted a late check out, it is only one or two hours extra past 11:00. If you have a 9:30 a.m. ressie at CM, exploring CR afterward, and you're using bus transportation, I don't see you getting back to Pop much before noon. Even with a 1:00 late check out, that doesn't give you a lot of time to pack up.
Pop will transfer your bag from Pop to AKL, but there is no guaranty about when you'll get that bag. It will likely be in the very late afternoon. If I had a car, I'd just throw it in the car. That way you'll have what you need when you want it (swimsuits, etc.).