For highest quality, render from AE to the Quicktime Animation codec. Comp in FCP, rendering to that codec again, then use Compressor to compress to MPEG-2 for DVD.
However … you won’t likely get real-time anything in FCP that way, since Anim is a high-data-rate codec. If that’s cool with you, great. If not, you should render out of AE to the best codec that will get you real-time in FCP: for example, the Decklink codec if you have that hardware, or Photo-JPEG, but that’s pushing it, IMO. Definitely not DV, unless you expect to do no rendering in FCP.
You could also do all your editing for timing in FCP in your particular real-time codec, leaving a slug for the graphics sequences. Then you drop in your graphics (rendered to your real-time codec from AE), then compress to MPEG-2 in Compressor. Unless you expected to do more effects in FCP, that would save you a compression (rendering) step in FCP, if I understand your process.
Anybody else?
Steve