You definitely can run the DOS versions of WC3 and WC4 on your Mac, via DOSBox. You just need to convert the CDs to disk image files, then mount those in DOSBox.
1. Convert CDs to disk images
For any other readers with an optical drive in their Mac, the built in application called "Disk Utility" can convert your CDs to images. Most guides assume that the images will have an ".iso" extension, while images created by Disk Utility have a ".cdr" extension, but they still work fine in DOSBox.
Tools definitely exist for creating disk images on your Windows XP machine, but I'm not familiar with them.
This guide recommends a tool called
ImgBurn, but I've never used it myself. If you install it and it turns out to be
full of Greek warriors who sack your city, kill the populace and burn it to the ground, I'll disclaim all responsibility.
If anyone else comments from personal experience with disk imaging tools for Windows, use their method.
2. Mount disk images in DOSBox
You need the IMGMOUNT command, so here's the
DOSBox Wiki on IMGMOUNT. Now, you could follow the standard route for lining up multiple images and swapping between them with CTRL-F4. I played right through
Gabriel Knight 2 using it. However, WC3 and WC4 both work if you just copy the files from the other CDs to the correct locations, as described
here. You still need to mount an appropriate disk image to get it to play.
You may need to adjust the DOSBox core, cycles or sound settings. Use the ones recommended on the
Wing Commander Tech Support page.
Too fiddly?
Even though you own the games, it may be easier to just buy them from
GOG. Those versions have already been put through the steps above to create a nice stand-alone launcher.