I think a a 3/4 ton diesel is overkill for what you have now....not that that's a problem. But as your kids grow, will you want to upgrade your trailer? If you think there's a chance, then go bigger.
And yes, diesels cost more to maintain. And, depending on where you live, the fuel costs more. My husband and I just had this discussion about the new 3.0 Ford diesel coming out, as I was thinking of getting a truck with that when it's available, but he mentioned how much oil changes etc. cost so I decided against that possibility. But I'm also only ever towing a utility trailer, not a heavy camper.
That being said, I'm a wife, no kids though. I would have driven our old F250 Super Duty as a daily driver without many issues. I would NOT have driven it if I worked in a downtown type area with tight parking though. Before buying my Explorer I also contemplated an F150 with cap as a daily driver too, it was very easy and comfortable to drive. An F150 would probably work with your current trailer, but probably not enough for anything bigger.
