They MUST save with PDF compatibility. It’s actually the PDF portion of the file that InDesign reads and uses.
Thank you! Do you know of any other settings that should be checked when saving the Illustrator files?
Do they need to embed fonts and color profiles...any other settings that should be checked when saving the Illustrator files?
Only include a profile if you need to make color managed conversions downstream. If the maps have specific CMYK values that need to output unchanged then don't include a profile.
Use either AI files with PDF compatibility or PDF/X-4.
Generally said, if you require vector files, ask for PDF/X-4 with layers (latest version), which allows you to turn on and off layers in InDesign.
Best formats are PDF/X-4 for vectors, PSD (in RGB!) for Images, PDF/PDF for images with text or vectors.