I like to use titebond 2,
It is just a modified version of regular yellow wood glue that can outlast the regular if subjected to the elements. As stated earlier, grain orientation is of question but of no concern for glue choice. I would use a yellow glue of some sort. I suggest that in all confidence. When it comes to clamping, just clamp the heck out of it. The more the better. If you only have a couple, you can clamp-screw-reclamp-screw-reclamp etc.. until you have that sucker solid. If you arent going to be real picky about it or dont have clamps (and your stands are kinda small) you can use old bike inner tubes...score a few from a bike repair shop for free. You can get alot of pressure going with them belive it or not. I learned that technique when laminating curves.
Oh yeah, when you are gluing them up, no matter how you are laminating them, you want to look at the grain direction of the end grain. To prevent warping you orient them like this if you had seven boards \ / \ / \ / \ not like this ////\\\ or /////// Ya know? that way if the boards do decide to move and they probably will, they keep each other in balance and you still have a flat surface.