I use two iPads and and iPodd Touch with one iTunes library and sync unique content to each device. You do not need to create a new iTunes library for the new iPad .... Assuming that you are using the same Apple ID on all of your devices.
When you connect any of your devices to iTuness on your computer, iTunes knows which device is which by the serial number and can recognize the devices that way. You can set you sync preferences any way that you want for every device that you sync to your iTunes library.
When your device is connected to your computer with iTunes running, click on the device name under the devices heading on the left. Then you can click on each tab in the iTunes window on the right ...apps, photos, music, books, etc....and select the content that you want to sync to that particular device.
Read this about syncing with iTunes
http://support.apple.com/kb/HT1386