Updating problems! HELP PLEASE

Hey guys, I currently want to purchase the OSX LION upgrade but cant due to some restrictions. I have 2 macs, a iMac I purchased a couple years ago and a white macbook I got a couple months ago. I want to upgrade to lion on both machines but my iMac is running on 10.5.8 and my macbook is running on 10.6.8. I can't get the mac app store on my iMac due to it being to old software and I dont want to have to pay $30 to upgrade to snow leopard only to pay another $30 for lion.

Is there a way I can use time machine to back up my macbook and restore it to my iMac? that way my iMac now has an updated software and I only have to buy lion instead the 2 software upgrades.