The Silverado won't have a rear centre headrest so only a harnessed can be used in the rear centre position (there are a couple boosters that could work but limiting to harnessed seats keeps it easy).
You said extended cabs, which have smaller rear doors and on the Ford will open backwards. The Dodge will have smaller rear doors but open like normal doors. I can't recall what the Silverado does, I think backwards opening as well. Our neighbour has an extended Ram as one of his main vehicles and regularly transports a boostered child, a forward facing child, and he's satisfied with the room and the spacing to get in the rear doors. He's got the 6 seater model and carries 4 adults and the 2 kids fairly often and it works for them.
Crew cab versions provide significantly more space than extended cabs and have regular sized rear doors. I recently bought a crew cab F-150 and it would be awesome for travelling with a family. There is tons of room in the cab. With an adult sitting in the back, a rear facing car seat and a booster, I can still stand in the back to buckle my rear facer. The amount of leg room for adults in the rear is insane; so comfy for long trips.
That being said, this is my truck, not a rental so I've got a carpeted bed liner which keeps my gear scratch free, and a hard tonneau cover for weather and theft protection. I also have a model with most every creature comfort and power running boards that are wider than typical running boards and extend lower so even my 2 year old can climb in herself.
The F-150 is really easy to install seats in though and due to the size of the back seat, two seats side by side is a breeze and fitting even a large rear facing seat isn't an issue.