I hesitate to ask, but is her footage so good that it does not require any editing (which would shorten it somewhat)?
A single layer DVD holds up to a maximum of 120 minutes including titles, transtions etc. A dual-layer DVD twice that. Your idea of a series of shorter movies is the best solution, and should fit on two or max three DVDs.
The application Roxio Toast (not free) has a 'burn to fit' option for videos longer than the prescribed maximum length, but there would be a degree of quality loss.
… My desire was to do some serious editing, but, they prefer all of the "raw" footage, warts and all. …
cheat your wife (this has a different meaning in English, right? )
this family reunion HAS some 'sorting scheme' - day1, day2, day3 .... or speaches, performances, party … or mommy, daddy, grandchildren ... or ....
split the 5h into groups - even more than 5 disks, create 8, or 10, or a dozen! in use, you can slide-in the DVD 'kiddies' to show how lil' cousin performs her cute ballet-dance with her dog, or the DVD 'Uncle Sam' with his endless hand-made poem about family-values , ... (or whatever happened on that party).
5h is half a day! nobody watches this continously.
and on each DVD I would add a 8min supercut with the best scenes of these family-reunion.-
you can edit short previews of what to come, add to a 'page' in the DVD menu, and, when using iDVD, you can add a text-box, cmd-K (red arrow) 'on Disk VIII' .... a.s.o.
a disk fits about an 1h of quality video.- so, on each disk 5-10 preview movies plus the extended, uncut version of such a section ...
=> finally, you DO edit the 5h down to a handful of minutes!
plus, for the brave souls, the 'raw', spread across some disks.