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Everyone has differing opinions on what they would take for a "lightweight travel kit" and you'll never reach a consensus quite frankly. I've had lots of different travel options over the years, including taking the whole nine yards, down to just a single superzoom. Personally, last time I went to Disney I took two bodies, a 24-70, a 70-300, a fisheye, a wide zoom and a 300/f4 AFS. Lugged a large bag around all day every day. I enjoyed it, but I knew going in I would be lugging a heavy kit around. If I went back today I'd likely take a small bag with a single camera, a 28/f1.8, an 85/f1.8, and maybe a fish, and make do with that. Lightweight and great optics at that weight. If I was doing Animal Kingdom I might take a 70-200 with a 1.4x or a Siggy 150 with a 1.4x... but for the other parks the two f1.8 primes would be my choice I think. Great for fairly normal perspective shots as well as some portraits/candids of the kids.
I've also used a Tamron 28-75 and IMHO it's the best lightweight zoom option because it's f2.8, optics are decent, and it's extremely light for an f2.8 zoom. But I certainly don't find the weight of a DSLR with a 24-70 overbearing either, so maybe for some that's a fair option too.
As I said, will be hard to find two identical perspectives on what makes the best kit for you.