As for space for your large family... that's a good question, here's how I look at it:
I'm going to attempt cooking for 50 people on the 4th on two 22.5"s. I'm only doing burgers and dogs, and they aren't the only thing on the menu so it's not as bad as it sounds. If it turns out I need more grill space, I can always fire up a third or fourth grill.
I'm thinking in your case, a second 22.5 could be the ticket. Let's consider area in this case:
18.5" grill = 268.67in^2
22.5" grill = 397.41in^2
26.75" grill = 561.72in^2
Two 22.5" grills = 794.82in^2
Ranch kettle = 1118.67in^2 (Weber says it's 1104)
Two 22.5" grills gives you quite a bit more than one 26.75, and 3 of them tops the Ranch Kettle. Hmm, maybe I will fire up a 3rd...
In my experience, 22.5" grills grow on trees around me. I found one in a dumpster, basically brand new. I found one on CL for $20, and I got one without legs for free from a friend who was moving. Less than 30 bucks later, that was complete too. I later made two of them into Golds for $40 each, but that was purely vanity. Even with that unnecessary spend, $130 for more space than a Ranch Kettle? Can't beat it.
If you're set on a performer, adding a 22.5" silver or gold, used, shouldn't be a problem.