Help creating a training plan for my wife

I've been tasked recently with creating a training plan for my wife. She doesn't have any aspirations of being a triathlete (yet...) but would like me to incorporate running, biking and weight training.

A little history - my wife used to be fairly active in HS but in college that dropped off (as it usually does). She had a skiing accident about 9 years ago and sprained her knee. It still acts up occasionally, so I want to make sure this is taken into account in the plan. I think with additional use and strengthening, her knee will be fine. She just needs to do something that will strengthen it.

She has been riding her MTB without issues, except that she took a nasty spill a few weeks ago and has been recovering from that (nasty bruises and a bum shoulder). She's almost completely recovered from that now. She has plans to ride the Tour de Tucson with me (she's doing the 40 miler with my brother-in-law while I'll be doing the century) and should be able to do it without problems.

We also routinely walk 4-6 miles hikes on the trails out here without problems, though the pace is pretty slow (2-3 MPH).

With all of that in mind, I'm creating a 28-week plan consisting of the following:

• 4-day run/walk mileage-based schedule - start with 4 min walk/1 min run (total of 4.5 mpw (1/1/1/1.5)); would like to eventually ramp up to 1 min walk/6min run or better (~15 mpw by the end).
• Biking 2 days a week (16-20 miles per ride).
• Resistance weight training 2 days a week (we just have a Bowflex but it works for us).

I may try to convince her to try a 5K or 10K after she builds up some mileage just to give her a goal to shoot for. I'm also thinking at some point I'll start rotating activity amounts after she gets a good run base (e.g. several weeks with more biking and less running, etc.).

Any suggestions that you more experienced folks have would be great! I know that she can handle higher miles at low intensity, but she wants to increase the intensity (walk -> run) over time. I'm building her mileage up about .5 - 1.0 MPW every 2-3 weeks (as the mileage grows, I'm holding the distance steady longer) and slowly changing the w/r ratio in favor of more walking. I have to balance boredom of training with over-training, keeping her knee in mind.

Thanks!