The safety on Club Pony Pals is outstanding. Every single message that a user ever submits, including their description (called status in review) and every message in the live chat is checked by an adult moderator, who is a real person. If someone enters an inappropriate message, it won't get through.
There is a lot of educational content. For example, there are math games that, if you get a score in the top 10 high scores for that week, you get an added Wiggins Bucks (game currency) prize. There are text based virtual "lessons" each week and at chat sleepovers aimed at developing writing skills.
The site encourages responsibility, budgeting, saving money, working for what you want and making sure you have the money to pay bills (in the form of monthly board bills on ponies bought from Olson's Pony Farm). It tries to teach that ponies are expensive and do take a lot of care. Ponies must be properly groomed before you ride them on the trail. You have to keep an eye on your pony's energy and hunger while riding, and be careful. A pony also has a "Health" bar - your pony will lose health if you feed it too many treats, hit things at a fast speed while out of the trails and if you don't visit your pony (ponies will lose one block of health each day they don't get a visit. However, if you have health supplements in your inventory your pony will be fed one a day while you're not there to keep it healthy).
I would definitely recommend Club Pony Pals - it is the safest multi-player horse site I've ever come across. To parents- if you have concerns about Club Pony Pals or just want to check it out before you'll let your child play, the admin staff encourage parents to take a look around or come on the live modeated chat and ask questions. You can also reach them easily via email.
Note: I've had to change "what other families should know" as the "safe" was changed to "safety is an issue." This goes for all of the reviews here. Ignore if it has the "safety issue" button - It is most definitely not! Both safe and not safe were combined into this button.