What a cheapskate! Blanks are now incredibly inexpensive compared to a couple years ago.
Anyway, if I wanted to do such a thing, here's how:
Reauthor in DVDShrink and add both titles. (The movies must be on your hard drive). Backup with no compression. Then run that file through DVDRebuilder using the "Half D1" Setting. Full D1 is 720x480 in NTSC land, half D1 is (guess?) 352x480. So essentially you still have adequate bitrate for that rez. Half D1 is nearly equivalent to SVCD, a little softer than full DVD but not bad at all.
If you absolutely MUST have a menu, drop both titles in a DVD authoring app and make your menu. And don't ask about keeping submenus, not practicable.