Hi Hayley:
Whether you stay on property or off site, it sounds like you are planning a wonderful vacation for your parents. In general, you usually can find the lowest hotel room rates off site. A number of off site hotels also feature free breakfast and other amenities. However, staying off site can mean traffic to and from the Disney parks as well as a different level of quality.
There are a number of
benefits to staying on property. My favorites include complimentary transportation to and from your Disney Resort and the Orlando International airport as well as extended theme park hours. If you are considering one of the Disney property Resorts, look at the
Value Resorts, which feature the most affordable rates on property.
In the end, it sounds like budget is an important consideration. If staying off Disney property makes sense for this trip, I would not give the matter much thought. Your parents are in for a magical vacation and may enjoy the break heading to an off site hotel at the end of the day.
Consider looking at independent websites such as MouseSavers.com and working with a Disney approved travel agent, who can lay out specific options for you.
Enjoy the vacation.