This is likely to cause some confusion. The TSA will allow you to opt out of the full-body scanners but then you do need to undergo a pat down. Here are some tips for families on getting through security from the LA Times:
Body scanner: Everyone being scanned through the new machines must be able to walk into the device and raise their arms as instructed by TSA staff. This applies to 3-year-olds and 93-year-olds. No one is allowed to, say, hold a young child or accompany an elderly person through the scanner. Be sure to take everything out of your pockets, not just coins and other metal, before going through the scanner.
Special cases: People who are unable to stand and raise their arms to be scanned (but aren’t opting out) will be screened using a metal detector, Melendez said.
Child pat-down: If a child is 12 or younger and unable to proceed through the body scanner alone or opts out, then he or she is subject to what the TSA calls "a modified pat-down" search. If the child is older than 12 and opts out of the scanner, he or she is subject to an "enhanced pat-down. " The TSA, citing security reasons, has not provided details on either type of pat-down. But the enhanced pat-down is widely understood to include closer examination of genital areas. It is unclear whether the modified pat-down includes the genital areas.
That said, if an alarm goes off during screening by the new scanner or regular metal detectors, any passenger will be subject to an enhanced pat-down (except for those 12 and younger, who get the modified pat-down).
How to prepare: I suggest parents explain to their kids all the procedures that they may encounter as they pass through security, including the possibility that they may be touched by TSA personnel as part of a pat-down. Parents won’t necessarily be with their kids as they pass through the scanner or get patted down.
I also advise checking out the TSA's advanced imaging technology web page that explains – in pictures, words and video – what the full-body scan entails.
To learn more: For more on the TSA's take on the security changes, check out the TSA blog post "Pat-Down Myths and Facts." To read about the controversy over the changes, see "TSA body scanners still raising concerns? Here's why" and "Government holding firm on airport pat-downs and body scans despite deluge of complaints."