I'm not a dentist but a dental assistant. Brushing twice a day is plenty. Make sure your using a soft bristled brush. Since your using well water fluoride pills can be a good idea. However there are other methods of intaking fluoride. For example, most toothpastes have fluoride in them. And your right. Too much fluoride causes fluorsis which is a discoloration on teeth. Too be exactly sure I would consult your pediatrician. Most children begin seeing the dentist at age 3. But its a good idea to start taking them even earlier when you go for your appointments so they can see its not a bad place to be. Hope this helps.