Thanks for all your comments and advice.  A different doctor today
emphatically said "no!" to goats milk and suggested rice milk.  I'll try
many of your other suggestions as well - including not replacing milk at
all. He does drink tons of calcium fortified juice.  I've never thought of
watering it down - but that's probably a good idea.  The Dr. also put him on
2 Tums a day and he loves them!

Kelly