When I reassembled the headlight buckets on our 79 Seville, I also laid some fiberglass cloth over the cracks in an effort to help brace them up some. I figured that even if I epoxied the pieces together, the strain from the adjusters and springs and stuff would eventually cause the cracks to open back up. It's just insurance for not having to go back in there later. After everything was cured, I pained the buckets in semi-gloss paint to help hide the work. The work is still visible, but not blatently-obvious. For the driver and occasional local show car, it's fine.
The passenger side light bucket was pretty cracked up. I think that corner had been bumped earlier in the car's life and that was never repaired. Hopefully that'll never happen again, and I'm hoping my repairs hold through my lifetime. It's something I'd recommend you do, too. It's kind of messy, but you should only have to do it once.