In areas where cell phones work, they're the hands-down winner for being convenient. Having to leave the radios on is a primary disadvantage, not only for battery life but for hearing conversations that you don't want to hear. Setting up a call time probably works best, say on the hour or half hour you turn it on for 5 minutes (as long as everyone remembers).
The Talkabout-type (FRS/GMRS) radios work pretty well; use the distance ranges advertised to judge their power, not how far they'll really go. The 6-8-12 mile range ones are pretty versatile. Make sure they have a good number of "privacy codes" for each channel or you will get a lot of useless chatter.
You can find reasonably priced units that come with a charging cradle and NIMH rechargeable batteries; this is the only way to go as far as I'm concerned, though with NIMH batteries you do have to top up the charge if they've sat for a while.
If you use the GMRS channels, technically you're supposed to have a license. What they don't tell you at the store is that the licenses cost about $85(?) each. You can use the FRS channels without any license, but they are lower power. That said, if you get a license you will probably be one of the few who actually bother with this bureaucratic baloney. Unless you just want to gab constantly, I can't imagine why or how you'd be busted for using GMRS if needed.
The higher power units will have a low power setting, which you should use unless you can't get in touch. Set up your default channel and privacy code in advance, something easy to remember for both users.
There are times when these little units are very handy; but many more times when you'd think they'd be handy, but they're not. At any rate, if you have a Big 5 sporting goods or similar nearby, they often get name brand units with 6-12 mile range and charger for $30-40 a pair, so what's there to lose? Take them along, and if cell phones don't work, you have a backup way of communicating.