Returning from exile at end step
Yeah, they all enter the battlefield at once, but each trigger will be triggered.
When they enter simultaneously, they 'see' each other. If you have an Ally who gives lifelink, one who gives +1/+0 and one who gives +1/+1, the net result of them entering the battlefield at the same time would be +6/+3 and three instances of lifelink (which doesn't make any difference to just one instance, since it's not additive) for your three allies