Here is what I do in those cases:
1) Create your new collection with your slug and fields (ex: Activities)
2) Populate your new collection with content
For the list view:
Go to the dynamic list you wish to preserve the design in the page of the template your site is based (Escape) and disconnect the fields one by one, starting from the botton field, use the navigator for this, until you are allow to change the collection. (There is a lock which is gone after you disconnect all the fields inside of the collection list)
For the details page:
You have to do some copy and paste between the blog detail page (Escape) and the new detail template page from your new collection (activities) and again just change the fields to point to the fileds of your collection (activities).
That way you can keep the template layout your website is based on and you can have your own fieds and slug. I have to agree the templates are all very beautiful.
I hope that helps.