The Scriptures Help Me Understand the Importance of Making and Keeping Covenants
Be sure to look at the March 1998 issue of the Ensign.  There are three articles about covenant keeping, and I took some of my ideas from these.
Sharing Time #1:

Materials:

On the posterboard, draw a hill of dirt.  Cut a slit along the top part of the hill.  On the back of the poster, tape the envelope under the slit so anything coming through the slit will be caught in the envelope.

On the paper, print out the following sword and cut out.

Go over the story of the Anti-Nephi-Lehies in Alma.  They made a covenant (a deep, serious promise) not to kill anymore, and as a symbol of their covenant, they buried their swords in the ground.  Go over the raid on their city, and how faithful they were to their covenant, even though many died. Explain how they and their families were blessed by this action.

What covenants or promises do we make? Are promises hard to keep?

Possible answers could include: baptism, marriage, promises to our parents, etc.

Have some answers printed on "swords" and have the children "bury" the swords in the ground.  As a handout, give each child their own printed sword, and let them write or draw a special promise they would like to make and keep.

Sharing Time #2:

This would work well for a class sharing time.

Have some children bring in something very special to them.  Something they would never want to lose.  Have the children show the items to the rest of the children and tell why they love their special things so much.

Ask the other classes if they have something special that they would hate to lose.  Take a few comments.

Pull out a picture of Hannah, Samuel's mother.  (See the March 1998 Ensign for a great overview) Talk about how Hannah wanted a son so badly that she made a covenant with God that her son would be in the Lord's service for his whole life. She was blessed with a son, and when he was three, she let him go live with the priests so he could start his service to the Lord.  Samuel became a great prophet because Hannah was true to her covenants.

Ask the children if they think it was hard for Hannah to keep her promise.  Then, ask them if it is hard for them to keep their promises.  Talk about the blessings that can come from keeping our promises.