I've used the Mandara Spa at the Dolphin and it was one of the best spas I've ever been to. I'd book as soon as possible if you are going within the next 5 months.
I have done Mani/ Pedicures at the Grand Floridian. It is a very nice facility and you can stay there relaxing during the day after your treatment. I believe they accept reservations at 180 days. They may have some discounts if you have a Disney Visa.