New Mac= A new iPod? I don't want this to happen.

Can you guys please help me? So I have an ipod 4 and I got it 2 years ago. It is old and now extremely slow. So I have just got a new mac book air last month and I used to sync my ipod 4, and iphone 5 on to an old hp computer. I want to sync using my new mac book air however when I plug in my ipod, it says welcome to your new ipod. There are two boxes I am allowed to check. The first one says that "Set up as new ipod" and the second one says restore from backup. I want the ipod to be like this, as it is now and I am afraid that checking set up as new ipod would delete everything I have on the ipod. I don't want to restore from backup, I want to keep it as it is. Is it safe to check set up as new ipod, or is there another soloutation to do this because I really want to sync using my new computer rather then the old one.