there are seats in baggage claim. there are seats at the rental car pickup sites(outdoors). they are shaded, as they are under other roads. the rental car pickup sites are 3 to each terminal i have ever used, so you could plan to meet at the one nearest gate C-35, which is the furthest north stop.
if you want to choose to meet at the furthest south stop, you could get on the bus and ride down there.