This was such an easy project and it turned out so cute! I went to Target and bought 4 plain white ceramic mugs for $3.50 each. We came home and pulled out our stash of Sharpies and C got to work. I gave her one mug and one marker at a time. I told her who it was for and she told me what color she wanted to use. It was the sweetest thing, she was telling a story with almost every scribble and dot. "This is Harold and his purple crayon and the dragon" on Nana's mug since they had just read that story together the day before.
After she colored them, I let the ink dry for a while to make sure it was fairly set. Then I used black Sharpie to write "I love..." each grandparent on one side, and then "Love, C 2012" on the other side.
Then I put them on a cookie sheet (just in case) in the oven, and heated it up to 350. I let them bake for 30 minutes and then turned the oven off and opened the door to let them cool slowly before taking them out. The baking process is what makes the marker stay on permanently even when you wash the mug, though I would carefully hand wash rather than put them in the dishwasher.
After baking, I did notice some slight changes in color that I thought we worth mentioning. The yellow looks more like brown, and what was a vibrant lime green turned into more of an olive green. So if you're going to try this it might be best to avoid those lighter/yellow-based colors that could change or darken during the baking process.
The color that looks like a brown-orange on this mug, and the one below were both originally yellow :(
The olive-y green in this photo was formerly lime green :-/
Other than the minor color changes, this was a fantastic project. Clearly it's best-suited for a child you trust with a Sharpie. We took off her clothes and put her in the high chair for minimal permanent damage to anything in the house, but she was totally awesome with the markers. She was so into the craft itself that she didn't even attempt to color anywhere else but on the mugs. She did get some on her hands (and being a lefty, that's inevitable) but it came off easily with some rubbing alcohol on a cotton ball. Overall, it was totally toddler-friendly, totally heart-warming as a gift, and we can't wait for C to experience the excitement of giving such a special gift on Christmas!