Grovetender Druids

• WWizards of the Coast2015-08-25
  Official Ruling
  If a creature with a rally ability enters the battlefield under your control at the same time as other Allies, that ability will trigger once for each of those creatures and once for the creature with the ability itself.
• WWizards of the Coast2015-08-25
  Official Ruling
  When an Ally enters the battlefield under your control, each rally ability of the permanents you control will trigger. You can put them on the stack in any order. The last ability you put on the stack will be the first one to resolve.

Rulings via Scryfall