Here is a little hind sight tip I have to share.
I'm a photo enthusiast and sometimes I over think how I want to capture photos while on vacation. I know that there are some of you that don't have the gear I do so it isn't a matter of choice, but before you go out and buy that really expensive lens to get your vacation photos think about what you will do with that lens after your vacation. Is it going to just sit around and not be used? If you don't take lots of photos then you probably don't need expensive glass. You will need good glass yes but don't break your trip budget by buying that $1800 lens.
My thoughts now are that I had a really good lens and I debated about taking it with me or leaving it home. In the end I left it at home in favor of a more pro glass. I also 'limited' myself to three lenses. I forgot that I wasn't on location and I probably more than likely won't do anything with the photos I took. I think I got to wrapped up in good glass and better glass. The lens I left at home was a perfectly good lens and it would have worked wonderfully in most situations I found myself in.
So if you are planning that once in a lifetime trip and want to bring back good photos and only have a kit lens for your DSLR then by all means upgrade to something more versatile. I have an 18-250 lens, this is the one I left at home.
I carried a backpack full of heavy camera gear and my laptop. So when we 'moved' from place to place I had to make sure that my backpack was someplace very close to me. I didn't take the backpack everywhere I went so that meant I left my camera gear in the hotel room from time to time and worried about it the whole time I was away.
If you have a good point and shoot camera then if you are with your family than this will do a good job for preserving your vacation memories.
If you think you need that 'great' lens for your vacation because all you have is the kit lens that came with the camera just remember in the past people took wonderful photos on vacation with brownie cameras. That expensive 35mm camera probably only had a 50mm lens on it and everybody was happy with the results.
If you want to upgrade then by all means you should. Good glass is heavy so be prepared to carry more weight.
Just remember the worst photo ever is the one not taken.