And I agree about the watercolor pads - but one caution on that: There are different surface types of this heavy paper, basically "hot press" and "cold press." The cold is lovely and a little bumpy, so your stamped images won't be as clear. The hot is smooth, so you may find it easier to stamp on.
And of course, you already know that you should use archival (permanent) ink on the stamp, so it won't dissolve from the water-based paints! Looking forward to seeing some samples from you in the gallery!