Since I sell these daily, I suppose I'm qualified to give a quick run down on them.
You REALLY need to watch what you shop for. Some cheap models may only be 14 channels FRS w\ slim to no squelch codes (aka Quiet Codes). Those same models you'll be lucky to get 1\4 mile out of.
Today, just about anything rated over 2 miles is sure to be a FRS\GMRS or straight GMRS radio. FRS = Family Radio Service and transmits at a maximum of 500mw. In lab perfect scenario's, you can get 2 miles out of them. Anywhere else, figure maybe a mile max and ultimately in reality, don't count on an FRS for any more than 1\2 mile. Radio Shack (Tandy, actually) started the FCC petition in 1994 for a "high power" license free set of radio channels. FRS is what they got. Prior to that, "walkie talkies" were basically limited to handheld CB or 49mhz, which you may have been able to transmit to your next-door-neighbors house with, maybe.
GMRS on the other hand is FAR more capable. GMRS stands for General Mobile Radio Service and exsisted for quite a while longer than FRS frequencies. GMRS radio's can transmit up to 5 watts and are allowed to use removable antennas (FRS antennas must be fixed to the transceiver). One significant thing to note, GMRS DOES REQUIRE A LICENSE! Now, is the FCC going to come to Disney and hunt down your family, probably not. Unfortunately almost all of the Big Box Stores (IE,
Best Buy, Sears, Circuit City,
Walmart, etc) don't really care and do little to alert their customers to knowing this. Sure, it's in the manual, but if anyone here at Dis is anything like my customers, maybe 1 out of 10 people actually read the manuals. The license will cost you $80 for 5 years and is renewable. The license will supposedly cover your entire family's radio "system". However there is a small catch that even the FCC can't get straight. GMRS licenses have always been granted to individuals, not equipment. Meanwhile on their site, they say a GMRS license covers the family's radio system. Anyhow...
If you're out shoping for a set of radio's for Disney and you don't want to spend a ton of money, stick to the big box stores. What you mainly want to look for is;
Quiet Codes (Squelch channels) - The more "codes", the less chance you'll have someone on your channel. As an average, you'll find 38-99 codes. Motorola currently has one with 121 channels.
Power output - The higher the power output (stated in wattage), the further you can reach with it. 500mw-1w is average. 2w is great and typically what you'll find as a max. in consumer level radio's. 2w radio's are typically sold as "12 mile" range radio's. Please, don't believe the package. To be realistic, in average use, take the number on the package and cut it in half, if not by 2\3. Unless you're using them out on the Bonneville Salt Flats, you'll never get anywhere close to the advertised range.
Channels - The number of channels, typically the better. 7-14 is very common, with 22 starting to become the new norm. To give you an example, if you were to buy a set of radio's with 22 channels and 121 squelch codes, you would have a maximum number of 2,662 channel combinations (22 channels x 121 squelch codes per channel). Basically, if you have your radio set to channel 14 and your quiet code set to 97, you won't here anyone else on "your" channel unless they have their radio's set to the same exact settings. Buying the latest and greatest radio with a high number of squelch codes can be a big plus, mainly because 121 code radio's are fairly new. Their might only be 5% of the people in the park with radio's that can go past 99 for the squelch code, thus giving you a better chance of having "your own channel".
Hope this all helps.
We have always spent so much time lookingaround and waiting for eachother when we split up. Now we both have nextels so YAY! 
no more looking for eachother. 
that's too cute.
