Teaching Tithing

If you take a peak at Facebook on occasion, you know we've had trouble keeping our eldest in bed at night. A marvelous friend gave us:

The Penny Suggestion 

Place two pennies outside the door. Each time he comes out, he looses a penny. 

Well, The Boy is no dummy and he caught on pretty quickly. He's also smart enough to make sure we put out pennies every night. 

We had a bit of trouble getting him to keep track of his pennies. A hole in the lid of the jar and the lesson that money can buy things seemed to fix the problem.
Last week we let him "buy" a date at the movies for ten pennies. He's already got more than 10 pennies this week and he wants to go buy a hot dog (not just ANY hot dog, but the kind that come on a stick).

Now that he's figured out money buys things he wants, I figure it's a great time to teach about tithing.
The Hubs and I are big fans of the Law of The Tithe, what with it's accompanying blessings and all. :D

I found three ideas on line which I think I'll incorporate along with the whys and hows of tithing throughout the coming week. In addition, we're going to go over splitting our money up into "tithe" "save" and "spend".

I wonder if any of you have some suggestions for me? Because this is the first time we're teaching a new principle, I'd like to do it right!