Coffee -- we use a #2 Melita (I think it's a #2, it's a small one). Just put the coffee in, heat the water, and pour it through. Some people like a French press but IMHO those are a PITA to clean.

On the flotilla aspect and keeping up: Don't sweat it. Don't even try. Schedules are a buzz kill when it comes to sailing. We've done the flotilla thing and we've done the non-flotilla thing. Our experience is that the best vacations are the ones where you are NOT committeed to going everywhere as a group and instead, just bounce off one another every couple of nights. Everyone has different things they like to do and places they like to go, and trying to get five boats to agree on a schedule is nuts!