Hi !

That's definitively a good idea to give violets a try ;o)
About odorata under a tree: better not a conifer and pay attention there's enough sun :-) During spring time, the more they'll have sun, the more they'll make blooms.
About Marie-Louise: a pot :-))
Anyway, don't put them together.
Really hope you will sucess, but don't worry too much, there's no reason why you shouldn't, odorata is so easy :-)

All the best :-)
Thierry.

How are your violas? Try an eco-lawn - must remark - they are long-lived and adaptable. Cymbidiums love the eco-lawn also.

Here is a link that might be useful: Growing Cymbidium Orchids - Various Societies