I'm 30 years old, and I grew up with Salt N Pepa. In fact their album Black's Magic was the first CD my mom ever bought me at age 10. My mom was always very open about sex, and the song Let's Talk About Sex lead to us having serious conversations about sex and sexual responsibility, which certainly made a positive impact in my life. The song is not about the mechanics of sex and does not promote sex, but talks about sexual responsibility and possible dangers of sex. The album also contains message of female empowerment and how to respect women and treat them properly, also very positive messages.
As their career progressed, their lyrics became somewhat more risque, but never overtly sexual. Although Shoop definitely contains innuendo, they never discuss the sex act itself in any of their songs (except possibly Sexy Noises Turn Me On, which does not appear on this compilation, but even that song never mentions any body parts by name haha). The compilation also contains Whatta Man, which describes their ideal man, including how such a man should treat and respect them, and how less than worthy men should be avoided.
None of their albums, including this one, have ever carried an explicit content warning, as the language is simply not bad. The only possibly questionable song on the album is None of Your Business, which contains lines such as "And if she wanna be a freak and sell it on the weekend, it's none of your business" which may condone prostitution, although the most prominent message in that song is that we should not judge other for what they do in their personal lives, because one's personal life is just that. Personal. Although this song appears on this best of album, in recent years Salt has renounced that song and they no longer perform it in their live shows.
Less open minded parents with less mature children than I was would probably object to allowing a 10 year old to listen to this album, but by 14, most kids have learned plenty about sex from their friends (regarding the message that everybody's doin it, I'm a high school teacher, and by the time I get them in high school, most of them have already had some sort of sexual experience, so they aren't really off there. I think the purpose of that message is to denounce the stigma that sex is taboo, and that when people are responsible and proceed with caution, it's nothing to be ashamed of. The fact is that kids are doing it anyway, so they might as well have good role models that are honest about both the joys and possible consequences of sex), so the positive messages in Salt N Pepa's work definitely outweigh the small amount of somewhat questionable material.
Overall, I think this album includes some of their best and most socially responsible work, and is excellent, but let's be perfectly clear, I've been a huge fan for 20 years, so I am somewhat biased in their favor. Although I am not a parent yet, I think I'd let my kids listen to Salt N Pepa.