Hello Paul!
My case is similar to yours. I had a T3 tumor in my tongue and had a partial glossectomy and neck dissection. No cancer was found in any of my nodes either but I will say that one of my margins was not clear and they found three 'stray' cancer cells outside of my tumor so I had to have a second surgery to get a clear margin on that side. So....I was told that there was a 1 in 5 chance that I have any more stray cancer cells in my body. So basically, the odds were in my favor that I wouldn't need radiation. However, it was strongly recommended just to be sure there wasn't anything else lurking anywhere in my head/neck area that could grow. I went ahead and went through with the radiation but it was a very tough decision to say the least. My feeling was to go ahead and do everything I could and that they recommended to try to have a cancer-free life.
Jessica Tar is a Head and Neck Cancer Advocate who also had tongue cancer that was stage 2 like yours and didn't have radiation, just surgery. Anyway, you can Google her, just for a perspective.
Good luck in your decision!