SOFTWARE REVIEW : Filling Summer Days : A variety of well-designed computer games and adventures can educate and entertain children and give their parents a break.

Summer lasts 94 days, from June 21 through Sept. 22. For mothers with preschoolers at home, it’s twice that long.

That’s because children 3 to 5 can bend the laws of relativity. Time slows down when it’s punc tuated every 60 seconds by calls for food, entertainment and grooming service.

Legos, crayons, train sets and the rest were invented for mothers, to give them a break during the long stretch from June to September. Now computers have been added to the maternal arsenal. But what can a 3-year-old do on a computer?

The answer is: quite a bit.

* “Putt-Putt Goes to the Moon” (Humongous Entertainment, $54.95) is the latest in a line of spectacularly well-designed adventures for tots. (The other titles are “Putt-Putt Joins the Parade,” “Fatty Bear’s Birthday Surprise” and “Fatty Bear’s Funpack.”) With beautiful cartoon screens and droll “hot spots” (click and something silly happens), these games create a seamless world kids can explore and control. Most kids prefer Putt-Putt to Fatty Bear. Older kids (5) will be able to solve the games’ central problems, but even 3-year-olds can wander happily.

* “The Playroom” (Broderbund, $37.50) has won awards from educators and parents’ groups for treating kids’ minds with respect while giving them a delightful introduction to computer power.

* “The Backyard” (Broderbund, $35). This sequel to “The Playroom,” shares its design brio and is chock full of loopy surprises. An array of nature lessons are gleaned from scrutiny of an ordinary back yard.

* “A.J.’s World of Discovery” (Bright Star, $49.94) is one of the best-kept secrets on the children’s computer scene: clever, cunningly designed, powerful and full of waggish animations. (Bonus: Inexpensive add-on curriculum diskettes are available when kids are ready to acquire elementary-school skills.)

* “Scooter’s Magic Castle” (EAKids, $49.95). In Scooter’s enchanted and varied world there’s always something new to discover. Parents and kids rave about Scooter. Even after a year kids can root out another secret or two from within this meticulously crafted entertainment.

* “Thinkin’ Things” (Edmark, $59.95). A distinguished manufacturer of early curriculum software designed this charming exploration game, which includes simple music, design and problem-solving activities.

* “Tuneland” (7th Level, $49.95). Howie Mandel’s voice enlivens this CD-ROM flight of whimsy, accessible to anyone with enough dexterity to click a mouse.

* “Mixed-Up Mother Goose” (Sierra, $29.95 diskette; $39.95 CD-ROM). Children help characters from their favorite nursery rhymes complete tasks. (Give Jack and Jill a pail and they can run up the hill and fetch a pail of water, etc.) Challenging for 3-year-olds, it’s a great introduction for kids 4 and older to the new breed of problem-solving computer games that will loom large in our kids’ futures.

COMPUTER ART CENTERS

Computer Art Centers’ open-ended play makes them ideal brain-building fun. And for Moms, no-mess art has got to rank up there with the invention of fire as a milestone toward civilized living.

“Crayola Amazing Art Adventure” (Micrografx, $59.95) is the latest addition to the growing field of computer creativity tools. Easy to use, it includes, besides the basic canvas with umpteen million gorgeous colors, a coloring book, dot-to-dot puzzles, paint-by-numbers, draw-and-fill features and wonderful sound effects. With some special drawing tools (a “crazy line” maker, a rainbow fill option and 16 “magic effects”), plus 60 animations, it’s as feature-packed as they get. However, it demands powerful hardware to run satisfactorily.

Another new arrival is “Colorforms Computer Fun Set” (Gryphon Software, $49.00). For Mac only, it’s a good choice for youngest mouse-clickers because of its simplicity. Besides the canvas it’s got copious stickers and background scenes. These allow anyone, regardless of drafting ability or hand-eye coordination, to create satisfying artworks. Also for Mac, the more powerful “EAKids Art Center” (Electronic Arts, $49.95), is a superb creativity kit that will satisfy older kids while working just fine for toddlers.

The classic art center is “Kid Pix” which has now been upgraded to the more powerful “Kid Pix 2” (Broderbund, $44.95). The granddaddy of this genre for home PC, it will run on older PCs yet remains an elegantly designed tool full of up-to-date surprises: silly sound effects, “hidden pictures” (revealed like gravestone rubbings), stamps and a coloring book. A companion to it is Broderbund’s “Kid Cuts” ($44.95), which requires a printer and offers a variety of cutouts and construction projects.

How many games does a preschooler need? (At these prices, whatever Mom and Dad can afford, and be grateful for it!) The nonprofit educational newsletter Children’s Software Review recommends 10 games altogether.

It may take a while to acquire that many. After collecting a few games, IBM and compatible users with four megabytes of RAM or more will want to install “KidDesk” (Edmark, $39.95). With “KidDesk” pre-readers can run their programs from a screen of icons, without waiting for Mom or Dad to enter commands.