Happy Adoption Day! ($15.95; Sept. 1996; 32 pp.; 0-316-55455- 3): McCutcheon pens a happy, easily sung song for the day a long-awaited child joins an adoptive family and ``a family was born,'' including musical notation so everybody can sing along. Paschkis's bright illustrations borrow from folk art to lend vibrancy to the celebratory mood of a book that clearly, straightforwardly, and lovingly answers a need for families built by adoption. (Picture book. 2-6.)