The conclusions drawn from the WHO report seem somewhat one sided the other side, the beneficial effect of sunshine is detailed here in SUNLIGHT ROBBERY:
http://www.healthresearchforum.org.uk/reports/sunlightrobbery.pdf
While it is true that the number and severity of sunburn incidents is associated with an increased risk of melanoma it is also true that more people suffer from a lack of sunshine and insufficient vitamin d status.
This research http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16872022&query_hl=16&itool=pubmed_docsum shows that 47% of girls in Ireland may have inadequate vitamin d reserves in the Winter and This research,http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=Retrieve&dopt=abstractplus&list_uids=15714215 using a slightly higher and more appropriate indicator of vitamin d insufficiency status concludes More than one-third of the adolescent girls have vitamin D status below 25 nmol/l and almost all are below 50 nmol/l. Two-thirds of the elderly community-dwelling women have vitamin D status below 50 nmol/l.
Rather than warning people of the dangers of sunbathing it would be better if you could advise them of the importance of getting regular but limited exposure to sunshine whenever they can, though of course stressing that getting sunburnt is always to be avoided.

Ted,

Balancing the benefits of Vitamin D (bone formation that prevents rickets in children) with its drawbacks (skin cancer) is a challenging public health question at this time.

Although only limited national data on rickets is available from a 2001 CDC report on this topic (http://tinyurl.com/7x2zj), 9 cases/million children were diagnosed with rickets between 1990 and 1998. 75% of these were African-American. The experts concluded that high skin pigmentation combined with low milk consumption (due to perceived or actual lactose intolerance) contributed to the high rates of incidence among this population.

For Caucasian children, the one expert concluded that 30 minutes /week of full body exposure (diaper only) or 2 hours/week of partial (clothed, no hat) was sufficient. However, there was insufficient data on African-American children to draw conclusions.

The panelists also concluded that for a healthy adult, a five-minute exposure (to one MED) 2-3 times/week is sufficient to stimulate enough Vitamin D production for Caucasians. African-Americans need 10 times more sunlight to form similar amounts of Vitamin D.

Using Irish data for U.S. exposures is an invalid comparison--Ireland receives much less sunlight than any state in the U.S. (except Alaska).

As for skin cancer, in 1998 there were 51,400 new cases of skin cancer and 7,800 deaths. The incidence rate for Caucasians is 14/100,000. This incidence rate is more than a factor of 10 (because there are less children than adults) greater than the rickets incidence rate. For African-Americans, the incidence rate is 2/100,000--again higher than the incidence of rickets.

Clearly a balance is needed between meeting Vitamin D requirements and skin cancer protection. However, the appearance of sunburn is not an appropriate benchmark for excessive sun exposure. A number of sources point out that the mechanism for the initiation of skin cancer is thought to occur at lower doses than sunburn (i.e. sunburn is an indicator that damage has already occurred, not a signal to go in.)

Based on the rates of cancer versus rickets and the ability to obtain Vitamin D through supplements or food, it seems that while both are serious problems, skin cancer seems the more dangerous of the two. However, the current data suggest different populations are more at risk for certain types of diseases, and these should be taken in account by qualified medical providers when evaluating the needs of a specific individual.

It has already been proved that sunlight is not harmful upto 2 hours after sunrise and 2 hours before sunset. Thus, common sense suggests that we use these window periods for getting our vital exposure. Unfortunately, the modern lifestyle (especially occupational work) does not permit such 'indulgences' every single day, which is sad, but fairly indicative of the progressive rot in modern society.