Need some advice, please!

[Jason Schmidt]

About 10 years ago, I was white hot about real estate, but then ... life, ya know?  Here is my situation: 

Next year, I'll turn 40, and I want to have my family of four set up well down the road.  Currently, we own two houses outright in the Houston area.  Our primary residence (zillow valued at about 190k) and our rental (zillow valued at about 155k).  The rental was really just for family, and "produces" $700/mo.  We have 40k in the bank and about 70k or so tied up in investments/collectibles.  

We are looking at possibly purchasing another house to actually move to, with a garage apartment or similar for my mom to move into, from the rental.  I had long considered just selling the other two houses and getting into a house that is 300-350k, and be done with it, but I am starting to think about having both properties as rentals.  The total approximate rent coming in from the two houses (according to zillow) would be about 3k a month.  

I would love to hear the input from everyone here - what would you all do?  What are your suggestions based upon my situation?  I'm happy to answer any other questions that need to be answered, if I have missed anything.  Thank you!