Most home editions seem to be around 690MBs. So yes a single CDR should be adequate.
BTW differences between the two:
The desktop CD includes a live system which allows you to try Kubuntu without changing your computer at all, and provides you with the option to install it permanently. This is the most common type of CD image that is downloaded, as the installation process is easier for new users. You will need at least 256MB of RAM to install from this CD.
The alternate CD allows you perform custom, or expert, installations of Kubuntu. It is required for setting up automated deployments, upgrading from older installations without network access, LVM and/or RAID partitioning, installing GRUB (Boot Loader) to a location other than the Master Boot Record, and for systems with less than 256MB of RAM.
I think it safe to say that Desktop CD is the better option here.