At VB the rentals are operated by Disney....there's no extra charge for towels at oceanside, so I'd say use the ones provided and just ask for as many as you need!
You're welcome. Only at HHI (of the 2 DVC beach resorts) are beach chairs not operated by DVC/TWDC). Hence the ability to use your KTTW card for payment and the supervision via Eb & Flo's.
We did take large beach towels on last trip just to have room to spread out on the beach - since we always get a 1BR or larger at VB just throw them in the washer and dryer for the next day