After doing what I had planned, here is the result, for the benefit of other:
(1) Do I have to suspend the activity at both the Master sites ?
-- I only did a suspend on the Mater Defenition site for that Master Group; that Quiescied the replication process on both the Master sites
(2) Will the DDL get replicated ?
-- Yes, the DDL (alter table add) did get replicated to the other Master site
I apologize for the wrong (or outdated) info in #2. That's one of the great things about this forum - there are plenty of people to correct mistakes.
Now, I'm still wonderin' if DDL propogation was available in 8.0.5? That is the version that I based my answer on when I worked with A/R. I recall, stopping everything and manually doing the DDL changes. This does not mean that DDL propergation wasn't available back then too. If anyone knows, please share.