If we want to ensure continuity in the committee's work, the majority of members should be present at all meetings to avoid leaving ground uncovered. If, for example, I always sent a substitute because I was tired, you would get pretty fed up.
In my view, if we say “only when a quorum is present”, we will be so restricted that it will be essentially impossible to hold meetings because, given the number of weekly meetings that we have planned, we will not always manage to have quorum. I therefore think it would be easier to work in small groups and, in the event of somebody being absent, he or she could read the clerk's notes and intervene at a later date.