You use a multigame DVD creator, there's atleast 2 that work. Search for them.
It creates one iso out of all the isos you want to put on the DVD which you can then burn.
And yes you can use different regions of games on thesame DVD.
I use GCMUtility to shrink the ISOs and GCOS Multi Boot for creating the Multi Isos. Most of the stuff I've crammed in there worked normally (I've done 3 Multi isos so far, with over 13 games on those), with the sad exception of Metroid Prime. ):