If you don’t want to deal with the limited options for public transportation, but just can’t imagine that long drive up to Dunlewey, it is also possible to hire a car and a driver.
Private Tours:
You can easily hire a driver to give you a private tour of Ireland. This will not be inexpensive, but may be manageable since you will not have the expense of the rental car itself and gas. If you have several people, a small group tour can be very reasonable. Searching for “chauffeur ireland” or “private driver ireland” will bring up many possibilities.
Point-to-Point:
If you are not interested in a tour, but just want someone to get you to the reunion area there are several companies that offer long distance point-to-point travel. Some examples are LfL Chauffeur Service and Optimum Chauffeur Drive. Examples of their current rates can be found here.
Once you have arrived at your destination you can rent a car at Donegal airport or use taxis to get around.