As my grandniece says: same! Some WDW trips have been very painful. Last three trips have been much more enjoyable, thankfully.
TP countdown says 60 days out for a walking regimen. Two months might be better than seven as you’d have less time to get bored and quit.
Mostly what you’ll do is walking and getting in and out of ride vehicles. The yoga would be great for the ride vehicle ability.
For the walking, I’ve usually, past trips, walked - trails in state park, indoor walking tracks or just around the neighborhood.
While you might do 8 - 10 miles a day at WDW walking 10 miles a week is probably enough to help you feel better at WDW. After all, most marathon runners do not regularly run marathon distances when they work out
Recently I realized that a lot of what we do in WDW is wait. We stand around. See if your employer will upgrade your desk to one of those stand up desks. The one my sister has will go up for standing work or go down if she chooses to sit. I think her employer also provides a matt to stand on.
I’d recommend also to go to a store specializing in sporting shoes. They can check to see what kind of stride you have and make suggestions as to shoe types best for your foot/stride.
I used to walk 5 miles several times a week. Always having sore legs and feet. Until I read about feet and stride types. Amazing what a difference the proper shoe makes!