Let me see if I understood this straight:
You have 4 videos 30minutes each and you want to have 2 audio tracks 30 minutes each on all of them.
That's 120 minutes of video and 240 minutes of selectable audio!!
Is that it?
But if so and if you're using 80minutes CD-Rs there's something wrong in your calculations when you say they'll be 250MB each.
250x4=1000MB
No 80minutes CD-R can hold 1000MB. 80minutes CD-R can hold 800MB!
And with 8 audio tracks overall your 4 video tracks will look bad for sure

Try 2 movies with 2 audio tracks in each movie at the most.
That's 60 minutes of video and 120 minutes of selectable audio.
And still I hope your movies will look ok even at low res.
Cheers