If you aren't able to find any stamp pads specifically for kids, then as long as your daughter won't put the ink in her mouth, I would think any brand of dye ink would be good for her to use. It's more washable than pigment inks and dries fast. Some brands of dye inks are Memento, ala Mode, Adirondack, and Rubber Stampede. Many stores carry their own brands, so just look for a dye ink. If you want to be extra sure to be able to wash the ink off hands, get a Craft Scrubbie from Ranger.
Inkssentials