Mom,
I am in your world (mid 50s here). I'll give you my opinion (which is worth what you are paying for it).
I like Preferred sites at Fort Wilderness because that generally puts us in loops 100/200 which is easily walkable down to the boat dock to get over to MK. We typically drive to the other parks (EP, HS, AK) so walking/internal transportation is not a question.
We do bring our bikes but they are for leisure riding around the Fort on our non-park days and not for saving us steps to the boat dock. Like you I don't pay for a golf cart (I have when my elderly parents have traveled with us but that's 3 times in 20 year) .
We tend to go to MK more than any other park so being in a Preferred makes sense for us. But if you using the internal Fort/external WDW bus system to go to the other parks, it's not much more walking to do so (although it is more time). Do you drive to the non-MK parks? Or use the bus network?
It occurs to me that the steps taken to get to a bus stop to go to non-MK parks (or the MK boat dock) is small relative to the number of steps you will take in the course of the day (especially in Epcot which is big/wide/spread out). When we go to MK, I think I wear out a pair of Dr. Scholl's inserts in a single day going from Space Mountain to Big Thunder to Buzz Lightyear to Splash to 7DMT to Pirates. <back and forth - you get the point>. But the steps in FW in a day IMO pales in comparison to the number of steps in a theme park (but I have no actual data to back that up).
So IMO what site type you have (Preferred vs. Premium) depends on what parks (MK vs. non-MK) you plan to go to and whether you will use Disney transport to the non-MK (internal/external bus or drive).
Bama Ed
PS - I have NEVER had a blister from WDW. Tired, yes. Flat feet, yes. Blister, never. I walk miles in my shoes regularly so that angle is not an issue for me.