Heya,
When you insert the installation disk there is an option to install bundled software. From there you can choose custom installation and only choose iWeb to install.
Is the load program smart enough to not load older software?
If you're smart enough to choose what to install then the program will be smart enough not to install anything unwanted.
Your Mac Pro and MBP installation disks that came with the respective computers are hardware specific. Meaning you can not use the Mac Pro disk to install bundled software from the disk on a MacBook Pro and vise-versa.