In August I'm taking the family on vacation from the UK to Yellowstone and southern Utah. The kids are 12, 11 and 8 and not big hikers. So it's primarily a family vacation but I also want to make sure it's worthwhile photographically - insofar as I can while looking after the family.
I have a Canon EOS 5D with 24-105mm L f4.0 USM and a Canon 100 mm macro lens. I do my processing on a MacBook Pro 17" running Lightroom and PS2, which I'll be taking along too, along with the LaCie Rugged 160 GB as backup.
With any luck we'll be seeing wildlife, so I'm thinking I'll need more pulling power than 105mm.
What further kit should I consider? I'm not a professional photographer but I can afford to make a reasonable investment in my kit, roughly at the standard of what I already own, by which I mean I probably wouldn't be interested in third-party lenses.