For RCI resorts, here are some that I believe have the option of limited shuttle bus service that your older teenagers could use by reserving the day before (most charge a modest fee)...
- Fairfield Bonnet Creek
- Fairfield Cypress Palms
- HGVC Sea World
- HGVC International Drive
- Sheraton Vistana Resort
- Sheraton Vistana Villages
- Sunterra Cypress Pointe
- Cypress Pointe Grandvillas
- Sunterra Polynesian Isles (I think)
- Orange Lake Country Club
- Cypress Harbour (Marriott)
- Royal Palms (Marriott, from MOWC hotel)
- Sabal Palms (Marriott, from MOWC hotel)
I don't believe the others mentioned are available through RCI, only II (like DVC/Disney's resorts, Horizons or Imperial Palms). Even if you don't know of a place offering scheduled shuttle service, remember that you can contact an outside shuttle transport service. Call the resort you get and ask whom to call. They may cost a bit more than routine service and stop at more hotels along the way than contracted shuttle service. But with a little planning, your older teens don't have to remain at the resort if you want them to be able to visit the theme parks on their own.
Also, if your resort ends up being very close to Disney property, your teens could take a taxicab to the nearest Disney location to your resort (such as DTD or Animal Kingdom Lodge) and use Disney transport to get to the parks from there. Reverse direction on the way home. The cab would not be using a parking space nor pay for the parking fee as they would if they drove to the theme parks. This may cost a bit more but at least it would give flexibility to travel when they wanted. If you'll be staying on Rte. 192, public buses will get them closer to Disney property, perhaps to a restaurant near the Maingate entrance, then a cheaper taxi ride in. If you're staying on International Drive, public bus/trolley will get them closer as well. All this requires patience, time and planning. But it offers options to younger people with no car.
FWIW, I would consider driving them to a DTD restaurant or a Disney hotel for breakfast, then let them take Disney transport for the rest of the day (resort and park hopping) until they make their way home by taxicab after the fireworks at night. HTH!