Here's one Unit's view.

This varies from year to year, depending on how many register. We treat all registered leaders as part of the committee. But, those registered specifically as MC have specific jobs beyond general planning.
This charter year, we have 3 MC. One is the pack treasurer, one is developing and will maintain a web page, and provide general background help, such as refreshment stand at pinewood derby. The other is our advancement person/popcorn chair/whatever else she agrees to help with.

We have several non-registered parents still with us who also function as traditional MC slots. They simply choose not to register for whatever reason.

• One oversees the planning for Blue and Gold.

• One is almost always available to be an extra adult at camp.

• One helps out with popcorn sorting and other background work.

Basically, whenever we can, we find something to draw the parents in. It may be as a helper to the son's den, it may be as a finder of craft items, it may be as a driver, whatever works to further peak their interest, we are in favor of.

In an ideal world, den leaders and assistants would only be responsible for their own den meetings and their "show yer stuff" parts of the pack meeting. The committee would handle the behind the scenes stuff and the business end of the pack.

We aren't there yet, may never get there, but we seem to be having fun as we travel the path together all the same.

Organize your pack Committee to make it easier for the parents of new Cub Scouts to fit into the Pack structure. One way is to create a bunch of subcommittees, each of which is responsible for some major function such as:

• Finance—could include the treasurer, FOS chair, fundraising team, budget team etc.

• Service Projects—would organize Good Will Good Turn, Scouting For Food, Chartered Org. projects, community projects, etc.

• Camping—organize Day Camp, Resident Camp, Scoutrageous, pack and family camp outs.

• Membership—organize Roundup, Charter renewal,  Webelos transition, Boy's Life.

• Recognition—handle advancement, leader recognition, applications for Summertime Pack Awards, Quality Unit Award, National Den Award, Blue & Gold, etc.

• Derbies—responsible for the equipping and organizing pinewood, space, rain gutter and other special pack races.

• Tours and Field Trips—makes the arrangements, files the tour permits, and leads a series of exciting pack activities.

• Communication—prints the pack newsletter, web page, organizes a phone tree or email list.
   

These are just suggestions. You can probably think of other subcommittees and other ways to organize.
Each family would be expected to supply a parent to be either a registered leader or a member of one of these subcommittees. This way, a newcomer to the pack would not  feel isolated and could take on a job knowing they would be part of a team that will give support and ideas.

It's important that every parent contributes in some way to make the pack go and to set an example for their sons to follow. Its also important that we help parents overcome any fears or misgivings about taking on these responsibilities.