I never used one of the launch tour companies, but someone has posted on the DIS previously that they had. Try a search, or try starting a new thread asking specifically about the tour companies, it may catch the attention for someone who has done it before and give you the pros and cons
We usually take our car and go to our place on the Indian River in Titusville where we can see the shuttle on the launch pad, watch it take off, and then get back to our car and out of the area as quickly as possible. Never takes us more than an hour to get back to Orlando doing it this way.
We also managed to get the causeway tickets directly from the NASA website last time. It was closer than our usual spot and was a fun day, but very crowded and made for a long day. You get bussed out there way before launch time, so bring folding chairs. Also, food lines are long (I waited for over 30 mins. just to get a cup of coffee from the coffee cart) so plan to bring your own picnic, much easier.
If your only choice is Grounds Tickets for launch day I wouldn't bother. You'll get a better view from Titusville (can't see the shuttle on the launch pad unless you have causeway or VIP/media tickets), plus you won't have to spend the entire day waiting for the traffic to try and clear. Also, it's a bad day to try and tour Kennedy Space Center even though the regular exhibits are open---just soooo many people!
Most important: PACK BINOCULARS!!!!