I believe cabanas are $40 a day. If it is imperative that you have one, you should reserve in advance. Umbrellas cannot be moved and they are limited - the best locations get staked out by 6 a.m.
However, you can go to Boss Frogs and rent 2 beach chairs for $30 for the week, walk 30 yds. up the beach, and plop down under a tree for shade. However, note that Keave trees drop thorns, so we were careful to brush the area around our chairs off before we sat down.
I just answered your previous question about luggage. You will have a washer and dryer in your unit at the WKORV. You absolutely don't need to bring more than carry-ons. We were at the WKORV for 17 days this summer and we did just fine with carry-ons and it was so liberating not to have any big pieces of luggage to check.
Here in my Hawaii Packing List:
Packing for Hawaii - Almost everyone takes twice as much to Hawaii as they really need the first time. We only take carry-ons now. Keep in mind two things - it is HOT and HUMID all the time in Hawaii and it is VERY casual. Even for a "dress-up" dinner you can wear a cotton dress or skirt, and an Aloha shirt and cotton slacks for the male. Most places, people even wear shorts to dinner. Don't bother with sports jackets, panty hose, evening wear, coats, dress shoes, jeans, or high heels. We usually stay some where with a washer and dryer near by, and plan to do a load of laundry every 3 or 4 days. This cuts down on clothing too.
This is what we take:
3 pairs shorts
3 T-shirts or tank tops
1 wind breaker or very light jacket/sweater/sweatshirt (for boat trips or Haleakala on Maui)
2 bathing suits
1 cover up
females - 1 or 2 cotton dresses/skirts (buy them there!)
males - 1 or 2 aloha shirts (buy them there!)
1 pair casual cotton slacks (wear on the plane)
SPF 15+ sunscreen, higher if you are fair skinned - critical! (buy it there)
hat with a large brim - critical! (or you can buy it there)
1 Pr. comfortable all-purpose sandals (that you can wear to dinner, or shopping, etc.)
1 Pr. water shoes (for the beach, boat trips, snorkeling)
1 Pr. walking/hiking shoes (tennis shoes - wear on the plane to save room in luggage)
Also, note that due to the wind and humidity, make up and elaborate hair-dos don't last in Hawaii. A hair-do that doesn't require styling, or hair spray, will hold up best, and no one really bothers with make up very much. If you are trying to pack light, don't pack any liquids. You will need a big bottle of sun screen and lotion, plus the usual shampoos, etc. Hawaii has major drug stores and grocery chains - just wait and buy your heavy and bulky liquids there. For after-sun lotion, we think Aloe Vera gel is the very best. It isn't greasy and it really soothes your skin and preserves your tan.
Hair tip for ladies - if you are going to the beach, or snorkeling, or out on a boat, for the day - in the morning, when you shower leave in your conditioner (don't rinse it out.) Or, wet your hair and smoothe in the normal amount of conditioner you would use. If your hair is long. braid it, if short, just slick it back. and then plop a sun hat on. After your trip, shampoo as usual. Instead of having snarled, sun damaged, dry hair, at the end of the day, you will have beautifully conditioned hair, that looks great for the evening.