Actually, there are paints and paint markers that are made specifically for already-glazed-ceramics. I bought a marker for only $3 and use it on thrift store dishes. You let them dry for 24 hours, then put the pieces in a regular oven and heat it to 300 degrees for like half an hour to heat set the paint, and then it makes them dishwasher safe.
I believe a few companies make these paints, but I got mine from the company Pebeo, and the product line is called Porcelaine 150. I got mine from Blick, but here's the link to the Pebeo website:http://www.pebeo.com/us/index.htm
Good luck! I think this is a great idea for Mother's Day! I might even do it myself!