Digital camera will work. A lot of artists take pictures of their work because it won't fit in a scanner, so it's common.
Just make sure that your lighting is good and your camera is on a stable surface so there's no blur, and turn the flash off. I've taken pictures of my large format stuff out in the sunlight, and that seems to work well (bright uniform and near-white light source). That works the best when it's something like pastel or watercolor, because oil and acrylic paints are a little shiny and that shows up when you have a strong light source as opposed to indirect lighting.
More than likely you'll need to touch it up and adjust the colors and brightness in Photoshop or whatever you use. But yeah, digitizing it with a camera is fine.