To replace the nutrients being missed, such as calcium, consult your physican or a nutritionist. For cooking, milk is unnecessary. It can be easily replaced with the alternatives listed, juice or even water. In frostings or other baking, substitute an equal portion of water or other liquid. I have used rice milk in some recipes as a straight substitute for milk, and had disastrous results.
Water seems to work better for pudding, and some baking.
Both are good for baking. Not all products have to be made from scratch. Bread is a special challenge for many, and there are pre-baked alternatives available. Rice bread, millet bread, tapioca bread, rye bread are all available. Ener-G Foods has many breads, including Raisin Bread.