Pat,
I recently read The Joy of Twins and Other Multiple Births.  It gives more
than the standard 3 positions for nursing 2 babies at once and also a couple
of ways of getting both babies into the place where you are going to nurse
them and to the breast without assistance.  The general breastfeeding
information is reasonably good, but a little misleading in places.  The book
has a lot of good ideas about planning for twins and dealing with twins in
general, especially in the first year.  It would probably be a good reference
for you.  Whether or not it would be a good idea for the mothers would depend
on whether or not they would consider it THE AUTHORITY on all breastfeeding
matters.  (If they would, I would not recommend it.)

Please do not quote me.  I recently reviewed this book for a professional
journal and am prohibited from reviewing it for anyone else.  Thanks.  Bonnie