The market for old Pentax lenses on eBay is very healthy. However, if they are just basic zoom lenses that aren't particularly fast (the longer zoom seems to fit into that category, the 24-70mm would also unless it's an F2.8 lens), those will probably not be worth much as basic slow zoom lenses are one of the most common lens styles out there and most people already have them.
If you put them on eBay, take a few shots of the lens from the side, top, and bottom (make sure you can read all the writing around the lens in the top photo), and try to be honest about the condition. Old lenses can get dust inside them occasionally, the lens itself can get scratched or pocked, etc. Also make sure that the aperture blades move smoothly, you can check this by taking off the front and rear caps and looking through it while moving the aperture ring (the one with the 3.5, 5.6, 8, etc numbers).
You can also look at current and completed auctions to get an idea of the value. If you have any prime (non-zoom) lenses, those will probably be worth more.
Good luck!