The 3105 is kind of small to use with a DDR pad, since it's only 1.5x1.5 inches. If you stepped on the edge or corner of the arrow it might not trigger, unless you built the pad in such a way that the entire arrow is resting on the 1.5x1.5" area. I would look into using load cells instead, and building them into the structure of the pad itself.
If you're still set on using 3105s, you cannot hook up multiple of them to a single voltage divider. However, if you want to cut costs, you can avoid using any voltage divider boards just by using a 1k-20k resistor on each 3105 to make a voltage divider depending on what output voltage you want (see the 3105 user guide for details). The voltage divider is only necessary if you want to be able to constantly adjust the output voltage of the 3105.