Children and adults alike will be entertained by the cast of characters, the challenges presented in the story, and the "non-essential" elements (hatching and training pets, crafting, gardening, etc.) of Wizard101.
Although there is some content available to players with a free account, the greatest enjoyment is to be derived by playing more of the game. There are several way to gain access to premium content: two of these involve having a credit card on file, and two involve purchasing game cards from stores which stock them (list available on the game's site).
Yearly memberships may be purchased by credit card; so may monthly ones. Or players may choose to NOT have a credit card on file, and instead buy cards to add to their accounts to either purchase membership for a specified amount of time, or to add "crowns" to their accounts so they can purchase unlimited access to specific zones.
I have thirteen different wizards on three accounts, in which I employ three different methods of maintaining membership: one is a yearly subscription; the second is a month-by-month, which I maintain by purchasing cards (a $10 card affords one month unlimited access; a $20 card gives two months); and my final membership is a "pay by zone" - I load money ("crowns") into that account via either credit card or game card, and pay a specific amount every time my wizard is ready to venture into another area of the game. Each method has its own strengths and weaknesses: the annual membership is a better value for players who play often; with either of the "monthly" options being next. The "pay-by-zone", though, isn't a bad choice - it encourages players to completely wrap up one zone before going on to the next; and if the player isn't online that often, this might be the best option, since it opens the zone for all players on the account, in perpetuity.
Many of the complaints in this forum about Kingsisle's credit card policies were written several years ago; I presume that changes have been made, since they have had my credit card info for 2 1/2 years now, and nothing untoward has happened. There is a master password on my account - which only I know - that has to be entered before I can purchase anything with Paypal or by credit card. This is a reasonable safeguard against anyone using my card without permission (though let me be clear: if I had a child or grandchild who used my credit card to purchase ANYTHING without my permission, the first conversation I'd have would be with the child, NOT the merchant). Do keep in mind, however, that such memberships renew automatically; if you don't plan to keep your membership, cancel before your anniversary date, or you WILL be charged - no refunds.
Your children will probably love this game - it's most appropriate for teens or older, but even younger kids can enjoy it. The best strategy would be to take the game for a test drive, yourself, before letting your kids loose in it [be warned, however: the game is addictive. More than one parent has wound up playing the game long after the children have lost interest!].
There are many good things about Wizard101: aside from affording canned responses ("menu chat") and filtered chat to protect younger players, it also fosters teamwork, offers opportunities for creative problem-solving, and reinforces the message that hard work yields rewards. It's an MMORPG, so players are apt to encounter people from all over the globe (fact: courtesy of this game, I have friends in all corners of the U.S., in the Caribbean, the UK, and Australia!).
The primary disadvantage to the game is the temptation to overspend: the lure of premium houses, gear, pets, and conveyances is hard to resist - and they don't come cheaply. It would be quite easy to spend $100 per month on virtual bling, if one weren't careful. And occasionally, the game can be quite buggy - although on such occasions, I fire off an e-mail to KI, and usually the problem is corrected promptly. The final disadvantage to the game is that (as in real life) a very small percentage of players don't act appropriately: that is to say, they cheat or exploit game glitches; they bully, or say or do bad things; nag other players to be their "girl" or "guy"; or beg for "gifts" . Players who feel they've been exposed to inappropriate behavior can report another player, to complain. Depending upon the type and the degree of the infraction, KI will either send a warning, restrict the player to "menu chat" for a specified amount of time, or ban the player from the game. Keep in mind that KI has access to all conversation logs from the game, and can verify/refute claims; they also take action against complainants who make frivolous or untrue accusations.
Overall, Wizard101 is a fun, safe game for kids (no matter how old they might be).