The 18-35 f/4-5.6 is an FA J lens. It is a pretty decent lens with full-frame coverage, but it doesn't have an aperture ring, so you'll be a little limited using it on a film SLR that doesn't have in-camera aperture control. Users report it is a good value, with reasonable sharpness and low distortion for the price.
The FA 28-90 is the best of the mid-90s midrange kit zooms, but that's not saying much. I got one not long ago on a film body that I wanted, and I much prefer the kit DA 18-55 AL WR. Check Pentax lens user reviews at
http://www.pentaxforums.com/lensreviews/SMC-Pentax-FA-Zoom-Lenses-c44.html.
I recently bought a K5IIs when prices came down to my budget after release of the K3, but I would have been happy with a K50 and would much prefer it to the Kr. It has greater sensitivity (ISO 51,600 vs 12,800 for the Kr); higher resolution (16.2 MP vs 12.2 MP); greater viewfinder area; and generally faster autofocus.
The weather resistance is valuable for a walkaround camera, but it only works if the lens is WR as well. Check the DA 18-55 that is being offered with the K50 and see if it says WR on the name ring and has a red weather seal set in the face of the lens mounting ring.
If the other zoom with the K50 is a DA 50-200 f/4-5.6 ED, either WR or not, it is okay for a kit lens, but you may not be satisfied with it after using it a while. It's not the sharpest zoom Pentax has in this range, and users (including me) report that its autofocus is slow in low-light situations.
As Pioneer suggests, take a look at the reviews of these two cameras and the lenses at PentaxForums. And Argenticien is right about getting a split-image focusing screen if you're going to be using manual-focus lenses. I had a KatzEye in my previous DSLR, a K200d, and it made it possible for me to focus my old M42 and Pentax K, M, and A lenses.