It's considered unusual, but not unknown, for terrorists to attack children. This particular terrorist warning implies that the attack might involve kidnapping. There are over 100,000 Western expatriates working in Saudi Arabia and they have been the targets of terrorists attacks. But al Qaeda, which is behind the attacks, is also directing attacks at prominent Saudis. Al Qaeda has always considered the royal family of Saudi Arabia (and all those who support them) as their primary enemy. Recent al Qaeda attacks have killed Saudis, and operations against al Qaeda has gotten police killed as well. If al Qaeda attacked Saudi scouts (many of whom are the children of prominent Saudis), the population would turn against al Qaeda even more. In Egypt, the Moslem Brotherhood incurred the wrath of the general public when some of their attacks killed children. This led to the Moslem Brotherhood being crushed (at least the faction that advocated terrorism).
The Saudi operations against al Qaeda in the past year has rounded up thousands of suspects. Interrogations have revealed a widespread al Qaeda network in the kingdom and further raids have uncovered large supplies of weapons, bomb making materials, false identities and communications equipment. So far, the al Qaeda operations in Saudi Arabia have not been much more than a nuisance, but the terrorists are aiming for more dramatic incidents. Attacking foreign Boy Scouts would be dramatic.
The U.S. State Department is currently warning American Boy Scouts (and others) who use certain recreational areas in the Saudi Arabia that terrorists were planning to attack these areas and seize hostages or simply kill people. The areas mentioned was very specific; Seven Wells/ Sherwood Forest (near Jubail), al-Rafiah Jebels, Capistrano Wadi, Bater/Brock Canyon, Qaryat Assufla, Petrifies Forest/ Mastodon Cave (near Nariyah), Wildcat Canyon, Bat'n Sabsab Dahl, Uray'Irah-Hamra Judah, Abu-Jifan Fort, Wadi Hanifa, Camel Caravan Road (near Muzahimyyan), Waba Crater (near Radwan), Hadiyah Station/ Hejaz Railway, Lake Lanhardt/ Dhahran Hills). This list of places was originally compiled by a foreign Boy Scout in the 1990s (you can tell by the misspellings). Scouting is very popular in Saudi Arabia. It was introduced in the 1950s and currently there are some 50,000 youngsters involved, plus adult leaders. Foreign scout troops are allowed to organize using their own uniforms and customs and there are several thousand of them there. The Saudi Scouts are prominent as volunteers during the annual Hadj (pilgrimage to the Moslem holy places.)