After last year's ill-advised adventure in elaborate preschool Valentines made weeks in advance (and the heartbreak that ensued when we found out that the class Valentines were not to be addressed to individual students, nor were they to contain any sweets), this year we made it easy on ourselves and did our anonymous cards assembly-line style.
I taped two sheets of 9-by-12-inch watercolor paper down on the table in front of the kid, and masked off six rectangles on each with tape, plus a border all around the edges. She just painted over the whole thing every which way (I painted some too), let it dry, then peeled off the tape and I cut them up into cards. Then I taped together some rubber letter stamps spelling out "THALI" and had her stamp each of them one night before bedtime; we untaped and added the final "A" at the end. Done.
She can write her name, of course, but I weighed the benefits to her of practicing her handwriting on twenty-eight cards against the possibility that it would make her mom go absolutely mad, and so she stamped.