Sea World and Busch Gardens are operated by the same company. I can tell you about my experience at BG Williamsburg last year.
I have an orthopedic disability since birth and use forearm crutches to walk on a daily basis and a wheelchair in the parks and at other places that involve more walking than I can handle. At BG we went first to guest relations. There they did a little "exam" to determine what rides I could go on. I had to show that I could stand, brace myself with my arms and legs. Then, they gave me a wristband and a printout of the rides that I was allowed to go on. Pretty much every ride required me to enter through the exit. Most times I was able to get right on with 3 other people in my party. For more popular attractions I was given a return time.
Do you have specific questions? What type of accommodations do you anticipate for your dad? I will say this-BG is nowhere near as good as dealing with guests with special needs as Disney is.