Wikipedia is no different than the Funk and Waggenel you used to look up naughty words in, or find some important information in.
Wikipedia is a source of whatever you seek.
If you seek the prurient, it's there. If you seek the wholesome, it's there. Rarely do the two cross, but they coexist.
Commercialism isn't an issue, as there are no ads, and the userbase works to keep articles unbiased. But discussion is frank, so if your child is naive or incapable of dealing with surprising and perhaps enticing new information, you might be advised to monitor his/her use of this site until they are old enough.