Possible Clues:

• Page in South America chart turned up, showing these?
• Grasslands of South America
• Dad's traversing peak of Moroccan plains
• Father’s banked millions, that’s plain
• South American grasslands
• Father and son crossing first of many treeless plains
• Ornamental garden plant — holding one, state politicians squeal
• Type of grass father's maintaining foremost in meadow
• Father’s taking motorway in vast plain
• Uruguay, in large part