Hi Tob, and welcome to the forum.
I have helped people with this a lot. What you need to do is in the Contacts app create your group. I recommend naming it something like ~Committee Name. (Notice I put a tilde(~) in fromt of the group name)..
Then click on All Contacts, locate the contacs that you want in your Committee group and just drag them over to the group name to populate the group.
Once this is done then in mail when you want to send an email to the group, just type the name of the group. This is where having the group name starting with a ~ makes things easier.
I hope that this makes things easier for you.