Sun damages skin—period.
The obvious trick in summer is to balance exposure to sun with protection from the harmful rays that cause skin damage and can lead to cancer. These rays are known as UVA and UVB rays, with UV standing for Ultra Violet.

Australian health authorities, alarmed by the skyrocketing rise of minor skin cancers and deadly skin melanomas have instituted a health campaign with the tag line: SLIP (on a shirt), SLOP (on sunscreen), and SLAP (on a hat).

Lets briefly look at the elements of the campaign.
SLOP: Many people tend to confuse the terms "sunblock" and "sunscreen". Sunblock fully blocks the rays of the sun and consists of such "blocks" as titanium and zinc oxides. They are extremely effective in blocking sunlight, but they also are colored and leave the wearer appearing like a character on the canvas of "Women of Avignon" by Picasso. Furthermore, they need to be reapplied after only a few hours.

Two sunscreens that have hit the stores this year, Heliolex and Anthelios SX provide significant protection against UVA (80%) and UVB (90%) for up to five hours after application. Helioplex is sold by Neutrogena as UltraSheer. They go on easily, need to be reapplied less frequently than sunblocks, and are invisible.

SLIP: Nothing blocks the sun better than clothing, and when the sun is blazing, make sure you put a shirt on to protct your back and shoulders.

SLAP: You don’t have to look like a kangaroo hunter, but the more you can put your face in shadow, the less harmful rays your skin will accumulate.
And yes, you can get a fine tan with all of the above.
Drill this into your kids:

SLIP on a shirt
SLOP on sunscreen
SLAP on a hat