Greetings, again, Johnrudy! Yes, you MUST go to Wakulla springs when you take your son to Tallahassee for the FSU visit. If there hasn't been too much rain, the spring will be crystal clear and beautiful.
The best thing you can do while at Wakulla springs is to go on the riverboat tour. It is so old-timey. The last time I went (a couple of years ago), our tour guide had such a thick drawling southern accent that some people on the boat from New Jersey confessed that they didn't understand a word he said. Ha! You will see alligators and cormorants and ducks and snakes and baby birds in the nest and fish and deer and maybe manatees and all sorts of wonderful spontaneous wildlife.
If you are adventurous, you can put on your bathing suit and jump (or dive) from the tall diving platform. The water is really chilly though.
As jensieblue stated, the old lodge is something to see. It was built Ed Ball, who was the founder of the St. Joe Paper Company, in the 1930s I think. It is simple, but beautiful, and Spanish in style.
Here is a really cool site about the Spring itself, with additional local lore information:
http://www.tfn.net/springs/WakullaSprings.htm
I am obsessed with springs in Florida, and I LOVE Wakulla Springs!