I think there is definitely a couple strategies at play here for you and your family. 

This campus hosts a large Magnolia home goods store, high end furniture store, cupcake bakery, coffee shop, gardening shop, live music concert venue, large grass area with toys and balls for kids to play with, an open plaza with eight food trucks, a small baseball field (that Babe Ruth once played on and families can now play on for fun), a restored historic chapel (the oldest chapel in Central Texas), and six boutique shops with men, women, and children's products.

Primary markets will continue to hold their value though tough to make them cash flow.

You're best off continuing what is currently being implemented and then making adjustments once you have a better grasp on the building.

I have a contrary play. 

Mixed-use continuation is best served if you have foot traffic there or if there may be local business who could use a storefront and there aren't a ton of other similar mixed-use options near by.If I was choosing, I like mixed-use better because it gives you a diversified investment inside of one investment.

The STR, if purely an appreciation play,  is speculation to me. 

That area is all full and our competition continues to build.

I’m going to continue to stick with midterm rentals something will open up soon.

I think knowing more numbers, heloc limit, plans and objectives for future goals all should play into "what is best".