My brother (13) and I (22) had never studied Latin, so we split on Latina Christiana I this year. We did not purchase the DVDs, but my impression is they woud be necessary if you wanted the students to study without your help and you didn’t want to give them the teacher’s manual. (Both my brother and I teach each other with the manual, but we have to carefully overlook the “answers.” And the CD is invaluable for pronunciation.)
We have enjoyed it thoroughly and been challenged by every lesson. We enjoy adding the history portion (comprehenson questions would be replaced by straight narrations for a more CM approach), but we’ve mostly ignored the geography—mostly because we’re not quite sure what to do with the maps or why.
Memoria Press Latin is grammar based, and I’m sure it would be more difficult if the student didn’t already understand nouns, noun cases, subjects, adjectives, predicate adjectives, verb tenses… There’s not enough information in the Latin course for an introduction to these concepts. (My understanding is that classically trained children get much earlier exposure to grammar and parts of speech than those educated according to Mason’s philosophy.)
In our case, Latina Christiana I was a good fit, and we plan to get Latin Form I in January. If you are interested, you can read two blog posts I have written about our experience with Latina Christiana I.
I would be glad to answer any more specific questions, as best I can…