Well, your strategy sounded fine--solid, creative, well-planned out--until you threw in "looking for a foreclosure." Where'd that come from? Why the heck would you be messing with that?
Foreclosures are unpredictable. They can take time. They're not necessarily the best bargains. And limiting your search to foreclosures really narrows the market greatly. Heck, even if 25% of the houses in an area are in foreclosure (and if they were, would you seriously consider living there?), you'd be ignoring 75% of the houses. Not a good idea.
Another possible weakness to your plan is the sale of the timeshares providing for the down payment. Sometimes you practically have to give timeshares away. Make sure you check and find out how much similar timeshares are selling for, just to make sure that their sale will provide enough for the downpayment.
Find a good agent in San Diego. One with a digital camera and digital camcorder. Have her search out properties that meet your criteria. Have her send you a slew of pictures and even videos on properties that may meet your parameters. You review them. Then have your sons and girlfriend view the ones you think would be possibilities, and have them provide feedback to you. Finally, if you think it appropriate (I know some people who would, others who wouldn't), go to San Diego for a personal inspection. I don't think that's absolutely necessary if you receive good information from your agent and good information from your sons and girlfriend. And, after all, they're the ones who'll be living there for the next 5-6 years anyway, not you. What you want to do is make sure that the house is a good value, and is likely to be a good investment over the timeframe.
One other thing: Have a contingency plan in place in case one of your sons wants to move out early. Or if some of the rent is dependent on the girlfriend, what happens if she and your son break up? You just have to have a plan on how to deal with that.
And check with a financial planner. There are various elements involved that would be of interest to a financial planner, and that could benefit you.
Hope that helps.