Hi Angie,
I haven't used either TOG or MFW, but have researched them both. Until a more experienced board member drops by, maybe I can help?
Something to think about for MFW is that it has separate programs for K/1st, children younger than 2nd aren;t folded into the main program. TOG co-ordinates all age groups within one teaching plan. MFW is more open and go and includes science. TOG requires more planning and has a bit more focus on the great books, primary sources, philosophy, and socratic discussions in the higher levels.
Personally, with your age group I'd lean more TOG. You can keep it light with their picture book suggestions for LG, and dig in deeper with your older dc (your oldest might be ready for the D level work) without having to switch between multiple topics.