Honestly, I've spent thousands on gear for my 90D over the years and most of these all-in-one zooms are pretty disappointing. I remember taking a basic kit lens to Glacier Park a few years back and every single wide shot had terrible purple fringing on the mountain ridges. It was a total nightmare in post-processing. Unfortunately, most lenses that claim to do everything end up doing nothing particularly well because the glass elements just cant handle the wide-to-telephoto transition without losing major sharpness at the edges. Tbh, it’s frustrating when you're trying to capture a once-in-a-lifetime view and the gear just doesn't keep up. Since you're on a strict timeline and budget, the only lens that wont drive you crazy is the Canon EF-S 18-135mm f/3.5-5.6 IS USM. Its got the Nano USM motor which is actually quite fast for tracking animals, though I found it still struggles in low light compared to my expensive L-series glass. If you want more reach for those Yellowstone bison, you might be tempted by the Tamron 18-400mm f/3.5-6.3 Di II VC HLD, but in my experience, the image quality at the long end is just too soft and muddy. I had issues with focus hunting on that one constantly and it was a mess. Stick with the Canon 18-135mm. The 18mm end is wide enough for the scenery, and 135mm gives you enough reach to keep a safe distance from the wildlife. Just dont expect it to look like a National Geographic cover. It’s a compromise, but for your budget, its basically the only stable option before you leave.