Depending on where you are on the spectrum in regards to the baptism issue, here's one simple object lesson idea. I don't know how many people you're working with, but you could have each family unit do this along with you as you explain it for greater participation. If so, you'd have to have precut crosses, a balloon, and a sharpie for each family.
Get a medium sized balloon, the lighter the color the better. On a small slip of paper cut in the form of a cross, tell everyone to write the word Holy Spirit on it.
Explain to everyone that after Christ died on the cross for forgiveness of sins, he gave the Holy Spirit as a gift to the church. You could discuss a little bit about the ministry of the Holy Spirit here, i.e. guiding us to the truth, reminding us of what Christ taught, convicting us of sin, sealing us for the day of
Then explain that the balloon is us. Upon baptism, God places the Holy Spirit in you. Roll up the piece of paper and insert it in the balloon. Ask if anyone can see the Holy Spirit inside the balloon. The answer should be, no. Now as we grow physically, and/or spiritually, blow up the balloon just a tiny, little bit so that it just holds its shape. We still can't see the Holy Spirit.
Then at confirmation, blow the balloon up some more, and shake it, the paper should rattle around. Most won't see or hear it, but you can say something like, "Through confirmation we start to understand a little more about God in our lives and we sense his presence more and more - an allusion to the Holy Spirit "bumping around" inside of us.
Then once we are confirmed, blow the balloon up enough to the point where you can start to see the piece of paper itself, we are saying we are ready to let others see the Holy Spirit in us.
Then blow up the balloon more and say something about how as we grow in our faith we are able to see the Holy Spirit more and more in our lives, by how we act and live as Christians. You could then tie the balloon, draw a smiley face with eyes looking up on the balloon so that the balloon now looks like
someone's head, and say, "And as we live and walk in the Spirit of God, He brings joy and peace to our lives (the smile) as we glorify him (eyes focused upward) in what we say and do as we bless others with the gifts and talents God gave us.
This is just the idea, if you like this idea, adapt and adjust it to fit whatever you are trying to communicate.
Pastor Jon Hayashi