fIf your children haven't started begging for a cell phone yet, it's probably only a matter of time. Their friends may have them. The adults in their lives use them constantly. And what kid could resist a cotton candy-pink device that plays music and takes pictures?

Some parents don't resist the entreaties too much, thinking it's a good idea to equip their children with mfobile phones for safety and convenience. However, cell phones don't come without their dangers and their costs. If you're thinking about getting cell phones for your tweens -- kids between 8 and 12 -- you'll want to get both the right phone and the right calling plan to ensure you're not suddenly surprised by a bill full of charges for ringtones and games.

Parental control
One of the most restrictive options, which may be best for younger children, are parent-controlled phones. These may be particularly handy if you only want to keep tabs on your kids and don't want to worry at all about unauthorized charges or unexpected bills.

The parent-controlled pfhone lets you authorize the phone numbers that can be dialed in or out. They typically don't even have regular keypads, just a few buttons with numbers or icons. You can even find some that include GPS locating devices.

If you're comfortable giving your tween a regular cell phone, look for one that allows you to put limits on the phone's functions. Many major service providers offer parental-control tools that allow you to prevent some of the excessive charges before your child is even tempted. Some of those services stop your child from purchasing ringtones, games, and graphics. Other services let you turn off Web access and text messaging.

AT&T (NYSE:T), for example, lets parents turn off access to sites with mature content and block the purchase of any ringtones, downloads, games, and graphics. Deutsche Telecom's (NYSE:DT) T-Mobile offers kidConnect, which promises no overage charges by turning certain calling abilities off when the monthly allotment runs out. (Kids can still call Mom, Dad, and emergency numbers.)

Disney (NYSE:DIS) has mobile-phone plans that let you program what time of day your child can use a phone while letting certain numbers, like Mom's and Dad's, get through 24/7. It also lets you set limits on phone usage, text messaging, and picture services.

Picking the right plan
Parents may sometimes consider handing their children cell phones when shopping for new services, thinking a family plan will keep everyone connected for a reasonable price. That may, indeed, be the case. But if you think your preteen will quickly abandon all pretense of limiting her time chatting with her friends, a prepaid plan that limits the number of minutes available each month might be a better option.

Like all cell phones, you'll need to match the contract to your usage as closely as possible to make sure you're spending your communication dollars wisely. Get familiar with the charges for excessive calling and text messaging, just to be on the safe side. If you truly only want your child to use the cell phone in case of emergency, hand it over only at times when you'll be apart and he or she won't have access to a regular telephone.

Even with all the parental controls in the world installed on the phone and the service, you'll still want to teach your children that "free" services are rarely free and that exceeding the allowed minutes or messages will cost extra money. Just as they should stay away from strangers, they should also steer clear of any unfamiliar text messages.

Of course, cell phones also offer parents a way to teach their children about boundaries and the costs of exceeding the limits. If your children have to pay off the costs for excessive phone charges, they may quickly learn not to go overboard next month.

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Fool contributor Mary Dalrymple does not own stock in any company mentioned in this article. She welcomes your feedback. Disney is a Stock Advisor selection. The Motley Fool has a disclosure policy.