iDVD is extremely limited; for instance, you can't even place precise chapters, only intersperse them occasionally in the movie by time interval. And there's no capability of individual Part of Title (Chapter) returns to the menu after they play. Heck, you can't even import Mpeg 2 video into iDVD.
You're going to need DVD Studio Pro to set up and program in what your client wants.
Really though, the idea of 'clients and iDVD' is pretty scary - you do plan to update soon? You knew that was coming, right? :-)
Best to you,
TFDVD Research Labs
Entering 10 years of full-time, professional DVD Studio Pro troubleshooting and support