For a stay of at least 4 nights but less than 8 nights, you get "Trash and Towel" service on your 4th day (check-in day is considered day 1). Housekeeping will replace your towels and leave more toiletries, another single-load box of laundry detergent and more dishwasher detergent, etc. If you stay 8 nights or more, you get a full cleaning on day 4 and T&T on day 8.
We just hang up and reuse our towels rather than wash them but that's harder to do with so many people in the villa. You will run out of places to hang up all those towels. So you will either have to wash them yourself or purchase additional towel packs. A Towel Package includes 4 bath towels, 2 hand towels, 4 washcloths, 1 bath mat. Last I knew the cost of a towel pack was $6. With 8 people, you would need two of them so it would be $12 for 8 fresh bath towels. For that money, I would just wash them myself. There will be one single-load box of laundry soap in the room when you check in so you will want to bring along some laundry detergent or buy some when you get there. They sell it in the resort store.