iMove / iDvd size incompatability

[mac2thefuture]

After spending ages making an iMovie i've now come to the burn stage so I can distribute amongst family members when i get this message.
Can I reduce the size without the quality?
Should I have seen this coming? Does iMovies tell you of expected volumes/issues as you build?
Thanks

 

[mac2thefuture]

iDVD predicts 7GIG - Finder says 1.8GIG??

 

[mac2thefuture]

I'm going mad here

Where is the best place to learn about imovie 09, idvd and now its seems i need to incorporate garageband to make chapters ???

Please