which kit lens do you have, the lens with or without IS? if you have the newer IS kit lens i would go with the 55-250 Is( mid $200) lens. the 75-300 you have is not reviewed very well (the other two are upper 8s to 9, the 75 is a 5out of ten). that way you would have a good lens to use from 18-250. you should be able to limit your lens changing depending on what you are planning on taking.( ie if you want a shot of the castle from the end of mainstr put on the kit) i would think you'd use the 18-50 most then the 250 for AK. i figure a vacation is only a week or two, get something you will want to use forever.
the other lenses mentioned look good as well and the build quality of the 55-250 isn't as good as the 18-200 but it's less than 1/2 the price( & rated really well which imo i'll take iq over build any day, haven't really seen any user reviews of the other lenses although i think the 270 got some good "news" reports when it came out if it'm thinking of the right lens). so if you want to spend $600+ you could probably pick up a low light sigma or tamron( ie 28-75 f2.8 around $400) zoom along
with the 55-250 and spend the whole wad but have 3 lenses. none of the zooms mentioned give you good low light capability which you might want for anywhere dark( ie rides) if you have the old kit( no is) i probably would still go with the tamron and 55 just for the extra 50mmdistance( but that is just me, i love as much distance as i can get) and the low light capabilities
i do use my 28-135 a lot, mainly cause it's one of only 4 working lenses i have at this moment ... and one is the old kit, which is not good, one is a fisheye, the other a 50mm: so not
much of a "decision" needed rotfl:


. but imo the 28-70 wouldn't be a bad walk around lens. i rarely
need to shoot much wider( or can't back up a bit) and 70 on a 1.6 crop isn't a bad range. if i am planning on shooting wider i just take a number of shots with a wider lens then switch lenses. calls for a little more planning but it's not
that much of a pain. i've actually enjoyed using my just 50mm for a full day a few times although at smaller aps. it's good enough to crop a lot and still be sharp.