Let me offer some food for thought. You dad is 75, and while none of us are guaranteed tomorrow, people in their mid-70s have fewer falls to look forward to than those of us who are younger.
If your dad draws either hunt, the two of you can enjoy a wonderful hunt together. Regardless of whether he kills the biggest buck living on the unit, a nice buck, average buck or NO buck, you can have a wonderful hunt together and create memories that have nothing to do with the size of the buck he might take.
Consider hiring a top quality outfitter and the two of you enjoy a wonderful deer hunt together. Even if you prefer to hunt alone, an outfitter can provide scouting, do whatever camp work you'd rather have his people perform, do as much or as little as you want... And the two of you can enjoy a memorable hunt together that you'll both remember for as long as you live.
Make the hunt about enjoying the entire experience and not just inches.