How to override the /taxonomy/term/% for specific terms? I would like to override the standard /taxonomy/term/% view for certain terms in a given vocabulary in two situations: one is for a given term, another is for all childs of a given term (so if and only if the current term has XXX has parent, the view must be triggered°.

When one of the condition above is met, then this view must be triggered, the standard view must be displayed otherwise.

What is the proper way to achieve this?

EDIT

Example: 
Standard taxonomy page orders teasers by published date and it is generally what I need except for all the children of the term "Regions" (Africa, Asia, Caribbean,...) where I need to order them by Country and provide exposed filters. 

I don't want to create a view for each of those terms. I would like to create a view that is triggered only when the parent term is Regions. In all other cases, the standard /taxonomy/term/% view must be rendered.
In D6, the taxonomy term page is themed by default with a function, but it can be overridden by creating a template in your theme called taxonomy_term_page.tpl.php (or of course writing your own function if you want).  

In D7, it provides a default taxonomy-term.tpl.php that can be copied to your theme and modified.

So, you would have to look to see what term is being displayed and if it's one of the ones you want customized, embed your view output for it; otherwise, let taxonomy do it's thing by default.

There is good commentary in the D7 template that should make that pretty straightforward.  In D6, there is a Crazy-Awesome Taxonomy Pages Video with Bob from Mustardseed Media that I found to be quite helpful but there you basically have a $tids array that you can look at to decide what to do.