If you're planning a family seashore adventure, here are some suggestions for making your vacation fun and relatively hassle free. SUN, SAND AND SHELLS

Everyone seems to purchase identical beach toys. To keep yours from becoming part and parcel of others' paraphernalia, label each toy with nailpolish or indelible marker before you leave.

A mesh tote holds lots of beach toys, and after you rinse them, they can drip-dry in their own airy sack. (Works for bathtub toys, too.)

Use net bags that once held citrus fruits or onions to hold shell collections.

Don't limit yourself to the standard beach toys. Use jello or custard molds and cookie cutters to make designs in the sand; measuring cups, empty bleach bottles with the tops cut off as scoops; old silverware, wooden spoons, cups and plastic containers.

Chidren's rubber-soled slippers take the sting out of hot sand. Plastic sandals or thongs also protect feet when the sun gets hot. Plastic sandals that buckle can be worn in the water to protect feet from stones and shells.

For added protection against the sun, use old T-shirts as cover-ups over bathing suits. They're not as bulky as beach robes and if they're stained by lotion, it won't matter.

Your infant seat can provide a comfortable place for your little one. An umbrella overhead will provide protection from the sun.

Crawlers can be restrained in a "sandbox playpen." Dig a shallow hole in the sand, then fill it with toddlers and toys shaded by an umbrella.

A playpen can partially restrain an active toddler and also offer a place for a comfortable nap. Place large jar-lids under the legs to keep them from sinking into the sand.

When the waves are too much for your toddler, compromise by filling an inflatable wading pool with ocean water. OOPS!

*Oil and tar stuck to kids or toys? Rub on peanut butter: It will dissolve the oil or tar. Wipe off the mess. Or remove tar with turpentine.

When the beach gets crowded, make it easy for your children to find you by placing a bicycle flag in the ground next to your blanket or by attaching a brightly colored scarf to the top of your beach umbrella.

In case your child wanders off, put the name, address or location where you can be found in a pocket or pinned to a bathing suit. Make it waterproof by writing the information with a fabric marker on a swatch of cloth.

Put meat-tenderizer paste on a jelly fish sting to ease the pain.

Sprinkle sand-covered kids with baby powder. Sand brushes off easily.

Place a shallow bucket of water outside the door to your beach house or motel room so everyone can dip his or her feet for an extra clean-up before entering.

Plan for rainy days and lonely evenings: Pack toys, records, books, cassette tapes and recorders, puzzles, games, crayons, paper, and pencils. SAND GAMES

Spell your name in the sand with footprints.

Treasure Hunt: Outline a small area in the sand and bury special trinkets for your children to dig for.

Open a "sandbox bakery." Use molds to make cakes, pies and cookies.

Take advantage of the ocean breeze by flying a kite or blowing bubbles.

Squirt guns and Frisbees are fun, too.

Save food scraps to feed the seagulls.

Have your children lie down so you can trace their outlines. They can fill in details with shells for eyes, seaweed hair, etc.

In addition to sand castles, create roadways, tunnels, buildings, mountains and sand sculptures of animals or faces.

An early-morning walk along the beach can supply the beginnings of a rock or a seashell collection.

Make seashell people or animals from shells, rocks, twigs.

Create jewelry by stringing shells with holes in them. Coat the shells with clear nail polish for a shiny effect.

Make a collage using shells, seaweed and rocks.

Indoor Shell Hunt: One person hides a shell, the others search.

Keep a seashore diary. Those too young to write can dictate their memories or record them through pictures.

BEACH BREAKS

Sitters from home may like to come along. Exchange babysitting for an all-expense paid vacation. Or, your realtor, motel manager or seashore neighbor may be able to recommend some reliable teenager to sit for you a few evenings.

Use this sitter during the day at the beach, too, so you can relax a little.

Plan a vacation with friends who have children close in age to your own. Not only will your kids have day-time playmates, but you'll also be able to trade off babysitting. Exchange afternoons off or evenings out. SEASHORE STRATEGY

When deciding on a beach location, select one adjacent to a well-known resort. It's the same beach, but you'll find that prices aren't as high and beaches aren't as crowded.

A few weeks before your vacation, make up notecards that list the packing necessities for each family member. Be sure to make a notecard for bathroom needs, too, and if you're renting a house, have a kitchen notecard. Not only will you be more efficient when it's time to pack, but you'll also have lists already made up for future trips. Update these cards as your family's needs change.

No room in the car for a portable crib, playpen or high chair? Consider renting this equipment when you reach your destination. Check in the "Yellow Pages" under "Rentals."

For those with pre-schoolers, an early-fall vacation is ideal. After Labor Day, the weather's still very warm, many rentals are half-price and the beach is less crowded. Another off-season advantage is that many of the shops in the area are also seasonal. Look for sales and bargains on bathing suits and beach equipment. SEASHORE MEMORIES

Once you're home again, fill an aluminum pie pan or a box lid with plaster. Before it hardens, have your child stick in shells, rocks, etc. that he or she has collected. Sprinkle it with sand.

athleen Touw is a local writer. This article is

adapted from her book "Parent Tricks of the Trade"

(Acropolis, $4.95).