Totally agree about the swapping nightmare. Unfortunately, big zooms are rarely as good as expected, but Canon EF-S 18-135mm f/3.5-5.6 IS USM is decent.

• Buy used gear.
• Get a UV filter.

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.

Building on the earlier suggestion, I totally feel your pain about the gear swapping nightmare. Honestly, I tried using one of those super-range lenses on a hike once and it was basically just a blurry mess anytime I zoomed past 100mm. It was pretty heartbreaking looking at my photos later knowing I couldnt fix them. Everyone keeps talking about the 18-135mm, but if you want reliability without needing a master degree in photography, you might look at these instead.

• Canon EF-S 15-85mm f/3.5-5.6 IS USM
• This one is super sharp and the 15mm end is way better for those massive Yellowstone landscapes than the usual 18mm.
• Sigma 18-300mm f/3.5-6.3 DC Macro OS HSM
• If you absolutely refuse to swap lenses, this gives you way more reach for animals, though the quality drops a bit at the long end. Whatever you pick, just grab a decent circular polarizer. It cuts the glare off the water and rocks and honestly makes the sky look way better. Dont stress too much about the gear, just have fun out there.

Adding my thoughts here. I remember my first trip to Zion with my 90D and honestly carrying three lenses was a total nightmare. I missed a bighorn sheep because I was busy swapping glass in the middle of a dusty trail. It sucked and I almost dropped my sensor in the dirt while panicking. Since you're on a budget and need that one-and-done setup, I'd be a bit careful with the really cheap kits. Here is what I'd suggest for Yellowstone:

• Look at the Tamron 18-400mm f/3.5-6.3 Di II VC HLD for Canon. It covers everything from wide mountain shots to crazy zoom for bison.
• Make sure to grab a SanDisk Extreme Pro 128GB SDXC UHS-I card too because 90D files are huge and you dont want to run out of space mid-hike.
• Be careful with the weight tho... these big zooms can get heavy after five miles. The 18-400mm is usually around $650 which basically fits your budget perfectly.