Hi Catherine.
I like the way you think. Getting your children in the mood for a Disney trip in advance is a great idea. There is no Disney World satellite radio station. The closest thing you'll find is Radio Disney which is Sirius XM channel 115. (I know this because that's the first preset on my minivan radio. We listen to it ALL the time.)
Radio Disney plays kid-friendly versions of pop songs for most of the day, with a segment for younger children from noon until 2:00 p.m. EST on weekdays. Radio Disney is a great, safe place for energetic music, but it's not really park related. If you want Disney park music, I suggest that you get some CDs for the car. A quick search on amazon.com for "Disney park music" brought up a number of inexpensive choices.
There are also a number of podcasts that play Disney music and discuss Disney news. If your kids are late elementary age or older, they might be interested in the some of the park news podcasts. You can find more information about this topic
HERE.
And of course I assume that you're showing your kids all the classic Disney films. Many of these can be checked out of your local library if you don't own them already.
Have a great summer getting in the mood!