There's cheaper software than Final Cut Pro that'll work just as well if not better. Premiere Pro CS4 is something like $700, Premiere Elements is around $80, Final Cut Express is $200, Sony Vegas Movie Studio (Windows Only) is $80, Vegas Pro is $600, Final Cut Studio is $1300 (and is now x86 only, but there's a workaround to make it install and work on a g5). If you really want to go all out, Avid Media Composer can be had for $1800 and works in Windows and OS X and has a lot of the features Final Cut will have working properly in a couple years now.
For something like you're doing, any of the above would work fine and be more than overkill. Avid would be my first pick, Premiere Pro 2nd, and Final Cut 3rd. Avid has less hardware support (as far as IO and special hardware) but guarantees the hardware that is supported to work and have by far the best support out of the three. With Avid you never get the run around that AppleCare is known for (transferring you back and forth, or being told that you need to call the hardware manufacturer etc), basically if the hardware shows up in Avid and is functioning (nothing physically wrong) they take responsibility.
Premiere comes 2nd because they have the most 'cutting edge' technology and are advancing faster than any of the others. Premiere Pro CS4 with the proper video card can render a sequence in a fraction of the time that same sequence would take in Final Cut (CS4 will offload rendering to the GPU and knock it out in no time, but only with a few select NVidia cards).
Both of the above work in Windows and Os X, and a license of either allows you to use the software in either operating system.
Final Cut is Os X only and as far as I'm concerned the only recent improvements they've been have been buying out other software companies and integrating their software the Final Cut Suite. Unfortunately they stop development. Apple bought out Shake (which was THE best effects program) and then simply stopped developing it. Awesome. They recently acquired Apple Color, which works great, just remember you need a proper display for proper color grading. As far as actual editing goes, Final Cut works fine.
Even iMovie/Movie Maker might work for you, but honestly when I tried to show someone how to use them (I figured it'd be simple) it drove me crazy how ass backwards everything seemed to me.