You should be able to mount the DVD with the following (change the paths/devices for your system):
mount -t udf -o ro /dev/dvd /mnt/dvd
You can then mount the ISOs as well with the following:
mount -t iso9660 -o loop /mnt/dvd/animage.iso /mnt/cdrom1
mount -t iso9660 -o loop /mnt/dvd/anotherimage.ido /mnt/cdrom2
You can the run the installers from /mnt/cdrom1/somepath and /mnt/cdrom2/some/other/path. I haven't got any ISOs on a DVD to test this, but the worst case should be that you mount the DVD, copy the ISOs off and mount them from wherever they are on the hard disk.