Does anyone know of any fun/romantic things to do in San Antonio?

My Husband is Graduating his AF Basic training. I got a room reserved at the gateway lodge. ( Does anyone know how much it is a night, the lady rudely hung up on me after I reserved them ) But I wanted to do something fun with my husband, I will be with his family. I know about the river walk and was planning on going there, but I will have 2.5 days. What else is there to do, that's not crazy off the wall expensive?