Colorful picture books and storybooks, a summer reading roundup; Three Days on a River in a Red Canoe, by Vera B. Williams. New York: Greenwillow Books. $8.95. (Ages 4-8)

A good deal of useful information is packed into this story of two boys and their mothers who buy a canoe at a yard sale, then plan and carry out a three-day canoe trip. The realistic child's-eye view of a camping trip, complete with mosquitoes and rain, has plenty of adventure, making it fun to read, while colored pencil sketches show, among other things, how to tie knots, make fruit stew with dumplings, and identify common fish and waterfowl. A good book for children in camping facilities, or those who yearn to try outdoor adven ture.