Preheat your grill on medium high heat for 10-15 minutes.
While the grill is heating, slice the avocados and peaches in half lengthwise and remove the pits. Brush a mixture of 1 tablespoon olive oil + 1 tablespoon fresh lime juice on the flat sides of each half. Make sure they're coated generously to avoid sticking to the grill.
Once the grill is hot, add the avocado and peach halves, cut side down, and close the lid. Grill for 4 minutes. Use grill tongs to carefully remove the peach and avocado halves to a plate.
While the peaches are still hot they can be easily peeled. If you prefer to leave the skins on, allow them to cool before dicing. Use a large spoon to scoop the avocado flesh away from the peel.
In a large bowl combine the remaining lime juice, shallots, garlic, and jalapenos. Dice the avocados and peaches into small pieces and fold into the salsa.