I agree that one of the entry level rigs will do in this case. I also agree that an all-in-one lens might be the way to go for you, and especially your wife at full auto. I don't have one so I can't say they are great, and many folks gripe about them, but I just finished thumbing through several of my Outdoor Photography magazines and I saw more than a couple simply outstanding photos featured that were taken with something like a 18-270 or 18-200. And they weren't ads either. I doubt the average person can pick out the differences between something shot with these as opposed to something nicer. In specific situation, like taking portraits with my 85mm or wanting to go ultrawide with my 16-35, the all-in-one will not cut if for me, but in your case, you just want to get the shot.
As another option, have you looked at something like a Nikon P7700 or P7800? I think they can shoot in bursts, plus they are smaller and probably cheaper than going with a DSLR and multiple lenses. In fact, I'm thinking about giving one a try. If I'm carrying my 16-35 and suddenly need more reach, or I'm out to 300mm and suddenly need something wide, a P7800 might be just the ticket to keep with me just in case. Just my 2 cents.
