Yes, you should tell any prospects for marriage that you are divorced. I see no reason to postpone it. Being honest up front will help you to more quickly find the wife that is right for you. Regarding the question of age, early 30's is certainly not too old for a woman to have children. Among the benefits of modern medicine, is the fact of improved prenatal care for both the woman and the child.
Women have children today much later than that by choice.
It is sometimes said that after 35, the possibility of problems increases, but that is not to say that a woman 35 or older will have problems. With knowledgeable and prudent prenatal care, many women are having children into their forties and in some cases beyond. I would just advise you to make sure that the sister does want to start a family and to make sure you discuss issues relating to that. As to guidelines for finding a wife, there are many hadiths, but the most important advice is to find a Muslimah of good character.