I think that's a very special gift! I don't know that there's a right or wrong size for place mats or napkins, but this might help --
http://www.pioneerlinens.com/placemat
http://www.nordicneedle.com/free/FRE...at_pattern.pdf
http://www.ehow.com/facts_5832438_si...h-napkin_.html
Please post pics when you finish! Love to see that tea party too! :D