I had the same dilemma, and fortunately, had great teachers for my son during the first two years of elementary school. (He was able to start the GT program in 1st grade, as well.) They divided the class into groups, depending on their skill level, so he was able to be challenged. Emotionally, I had to do a lot of praying. Finally, in first grade, he made a very good friend who was the same emotional level. We also enrolled him in sports, which kept both his mind and body active, plus it helped his self-esteem, being part of a team. I would definitely encourage you to find a sport your son likes. (My son clicked with martial arts - it involves serious mental skill, as well as physical exertion.) Sports help relieve pressure from being so smart that people expect a lot from you, and all the other stresses of just being a kid. :)
Also, if your school district won't start GT until the 3rd grade, I would just supplement at home. There are wonderful resources online. (Check out http://www.superkids.com/aweb/tools/math/multiply/.)
Good luck and good for you, for being such a caring, conscientious parent.
M. B