.cwk is an AppleWorks file. What operating system is your new MacBook running? Click

--> About This Mac --> Version: 10.x.x. If your machine is running 10.4-10.6 you can install AppleWorks through Rosetta. Otherwise you will be limited to opening the files in Pages provided you were running AppleWorks 6.x on your old G4. The latest OpenOffice may also be able to open these legacy files.