If your going to use frames also make a non-frames version.
Have something like…
[HTML]
| Code of first frame here | Code of second frame here |
[/HTML]
Obviously edit that with your own information.
The whole process is basically a cut+paste job. Like you said you can then optimize the non-frames page for the engines while affecting less than 10% of visitors.
Do what you like best in terms of looks. BUT if you want to use frames so you can edit navigation, banners or footers/headers by editing just one file you might want to try PHP or ASP. Much better.