Thanks for the guidance folks, I'll keep working with it.
I appreciate that there will need to be some cropping necessary, particularly as fitting an image within margins changes the aspect. In simple consumer software such as Apple Photo you can put off cropping until the last printing dialog and it doesn't affect the saved image. This completely overlooks the issues of resolution prior to printing, but then the target audience doesn't have to worry their pretty little heads about it. 8-) (yes, I'm in that target audience most of the time)
My desired flow for this particular case would be to
1) make a rough initial crop to clear out any obvious junk and define the initial composition
2) Make basic adjustments to the image
3) decide whether to print, how big, and what margins
4) adjust the crop to fit the paper size and margins, and
5) print
In all of this my only concern with resolution is that it is high enough for printing. If it is marginal I might want to fiddle with the sampling, and double check the result. I can see the need in some cases for validating the resampled result prior to printing, but that needn't be persisted for my naive usage.
I'm OK with the 4) being before or after I actually hit the 'Print' command; but it should be easy to make adjustments larger or smaller at that time. In particular I may make prints of different sizes or margins, and I would like to adjust the crop rather than start over from scratch. This would imply to me that cropping and sampling are independent.
I design UX for a living, so I understand that everybody has an opinion. I'm impressed that anybody listens. 8-)
Thanks!