I like valentines day activities because they lend themselves well to coloring, writing, painting, cutting, and gluing. My favorites are the heart butterflies and the heart bugs, but just drawing hearts and coloring and cutting them are great too. Making flowers out of hearts is a really simple way to do it, and a button heart flowers would be really easy to make.
Kids can be as detailed or as basic as they want to be with their coloring, and then you can write simple words about valentines day, or words that you feel about someone special. You could also have the kids write a sentence to someone they feel is special to them. I always like to glue my crafts to the base paper so that it is easy to add some writing to the activity.
I also made a cute clothespin game a few years ago called the sugar bug game. Clothespins can be a good way to work on finger strengthening (depending on the child and their motor abilities).