Well, this concept of streaming music from an iPod or iPad to your car's radio has come up before, so there are many other posts on this topic; searching will provide you some more information -
But regarding your BT option from the iPad, your car radio would need to have that same function, i.e. BT to accept the wireless signal, not likely with most car radios, but possibly included in more recent ones or as an installed add-on - not knowing your car or radio, I would just guess that you don't have that option?
Now there are FM devices that can attach to an iPod or an iPad and send out a FM signal that can be picked up by your radio - I had one in the past for an older PDA - was a piece of junk (threw away) - you can google these options, check Amazon, or search the forum (I've posted on this option); they might work or will be worthless, up to you to take a chance.
The final choice is to have a 'direct' connect so that you can simply plug in your iPod or iPad into your car's sound system - probably will need a professional installation but would likely be the best retrofit - you would need to check w/ you local car dealership or a place (like Best Buy) that deals w/ these installations - good luck and please report back your results -
