Welcome to the DIS!
I got my Pal Mickey in 2003 and I love him! (DH and I have no kids). He cost around $60, not sure if he is more now. There is a new version of him out for the Happiest Celebration on Earth. You can get him in most WDW gift shops, including at your resort. Make sure you have them activate him for you.
Each time you go through the tunrstiles into a park, Mickey will vibrate and giggle and say something that lets you know he knows where he is. When he vibrates, you can ignore him if you want to. If you want to hear what he has to say, you squeeze his hand or tummy and hold him up to your ear. Squeeze him again within a few seconds for a repeat.
Pal Mickey give you lots of info about the parks & attractions, tells you where characters are, when parades and shows are starting, and teaches you a few foreign language words & phrases in World Showcase. He occasionally surprises you inside a ride or attraction (very cool). He also tells lots of corny jokes and plays games, even when you are not in the parks.
One warning: When I took Mickey back to WDW for his second visit last November, I should have given him brand new batteries. He got "sick" the first time we entereed Epcot and had to go to the Pal Mickey hospital. The CMs were wonderful about "treating the patient" and charged me nothing for new batteries.