The most important herb for type 1 diabetics is gymnema sylvestre, which has been shown to help regenerate beta cells.  This herb is also a sugar blocker and can help prevent absorption of much of the sugar ingested after the herb.  The gymnema should be taken at least 20 minutes before meals to allow it time to lock up the sugar receptors.

Juniper berry or Devil's club (not Devil's claw) both function like insulin and will reduce the need for insulin.

Magnesium malate is also recommended for insulin production and to prevent insulin damage to the tissues.

If they can handle a powder I have had a lot of success with my Sugar Balance formula:

http://www.mountainmistbotanicals.com/formulas/sugar.htm