"you need to go with a Kindle Fire or other tablet if you want color. then you sacrifice readability outside in the daytime."
True -- and this is played up a lot in commercials for the Kindle PaperWhite. But I'd just encourage you to ask yourself how often you're actually wanting to read books outside in direct sunlight. If this is more than once a year during your vacation, then the B/W PaperWhite is, IMO, absolutely the best option. Extremely readable -- and easy on the eyes -- under any conditions.
It's almost never mentioned, but the PaperWhite is also able to do rudimentary Web surfing. It's slow and awkward, but it can be useful for looking up something quickly on Wikipedia, say, while you're reading. (If you have a PaperWhite and haven't used this feature, it's under Experimental in the drop-down settings menu on the Home screen. Which tells you that Amazon is still -- after six years -- treating this like a very rough beta.)
But if you want full-color, high-resolution photos/graphics -- if you think you might read a lot of magazines or children's books or books with color photos -- then I'd steer you toward either a Kindle Fire HDX or an iPad Mini with Retina. The Kindle Fire HDX's display is currently the best on the tablet market. But the iPad Mini is overall a lighter, more powerful device. But, honestly, either one will do the job for you. Just a question of whose ecosystem you prefer (Apple or Amazon), who has more of the content you're interested in, and which one "feels" right for you.
Bob