hi Tom, near Cap Cana is nothing affordable, you have to travel every day from accomodations to Cap Cana, i hope you guys bring your own car.
Cap Cana is the south end of the so called Punta Cana area, right aside is the Punta Cana Marina, Punta Cana Resort & Club, Tortuga Bay and Corales Punta Cana, all non-AI and all top notch, means expensive(i.e. small Presidente RD$160.-).
so the nearest spot(15-20 minutes drive one way) would be Veron, there you could stay at the hotel of the Parador Punta Cana, rooms are around $60.- per night, clean rooms, save facility, nothing luxurious or special.
otherwise you would need to stay in the Bavaro Area, i.e. in El Cortecito at the Cortecito Inn, rooms $60.- per night per room(you can be 2 in one room for the same rate), poolside breakfast included, and also in El Cortecito, across the street from the Cortecito Inn is the little family run guest house La Posada de Piedra, rooms also around $60.- per night.
if you find the time step by at the Punta Cana Marina and say hello, i have always some cold ones available(don't worry, not for the above mentioned RD$160.-, lol).
good luck
Mike