Here is a simple little valentine that you can do with your little one or make yourself. The design is based on these and these cards, and I think it makes a sweet valentine. It does take using a smaller, firmer brush so that you can make the heart shape. For younger kids, you could have them use a crayon or colored pencil. I think this kind of thing looks better with the imperfections, so no need to make it perfect.
Download the printable here. It makes 2 cards. Cut paper in half and fold.
If you like this, you should try this free printable heart Valentine. All you need is a brown bag for a sweet lunchtime surprise!