I would like to know what is the best treatment for seniors with type 2 diabetes?

Same. Depending on the age but in general, diabetes treatment in the elderly is the same as anyone else: diet/exercise, medications and Insulin if needed. We worry about low blood sugar in elderly so the dose might start out lower and titration might be slower. Depending on the age and the amount of medical problems, we might also make the diabetes goal less stringent.
Diet first. Proper dietary control is the mainstay of treatment for all diabetics. That includes the proper caloric intake to maintain a healthy weight and limiting carbohydrate portion size. If diet (and regular exercise) are not enough to control your blood sugar then there are many oral medications and insulin. All have pros and cons. Not one is best for everyone.