It sounds like your MIL needs bailing out of a piece of property she can't afford to keep and pay taxes on. Your husband will side with her if he has never had the courage to ever tell her no. It sounds like she needs to do the difficult, but smart thing - put it on the market.
Real estate is no longer the investment choice that it was in some states several years ago. If you have to manage it, pay taxes on it (not cheap in TX), then it is a very poor investment. If he really wants the property, he can bid on it from the current owner when he gets old enough to own property.
If she sells it and wishes to invest that money for your son, show her a conservative estimate of what it would be worth when your son hits college age.
I have one out of college and her college debt amounts to $600 a month (and that was with a partial sports scholarship!). My son's debt will be close to that when he finishes in a year and a half. We were only able to save up one full year for both. The food and lodging is what really adds up as they both attended schools away from home.
The government loans are a joke. They charge an arm and a leg to these poor college kids. Financial aid is another joke - whatever you qualify for comes in loans. Our daughter's school helped her a bit when my husband and I were both out of work, but my son's school gave us nothing. I realized that there must be kids out there whose families were even worse off than us at the time.
If your husband won't listen to you, have him talk to a financial adviser. Tell him that you just want him to be informed as neither of you are probably experts in investments.