Before you go to the Alamo go to the IMAX theater in the Riverwalk Mall - it's right across the street from the Alamo. Knowing what happened in that little mission makes a huge difference when you see it.
There will be tourists everywhere. The military base there adds to the people who see what there is to see. Hopefully you'll be there mainly during the week.
THere is so much to see there. Fiesta Texas and SeaWorld if you like that sort of thing. The River Walk is a must. Mi Tierra is a great Mexican restaurant pretty near the River Walk.
www.kayak.com is a site that uses multiple searches. We stayed at a La Quinta last time we were there - in March - there are several throughout the city. They include a pretty good breakfast - boiled eggs, instant oatmeal, make your own waffles - not just cold donuts and juice.
Look at the SAS Shoe Factory website. I'm on my feet all day and wear their shoes exclusively. It's a cute shop even if you don't buy the shoes.
http://www.visitsanantonio.com/index.aspx may give you some ideas. Your Great Uncle should know of places to go as well.
We were there last (in March) with two 3 year old grandsons. What we did probably won't be high on your list!