I plan to have them remove one each at snack time since that is primarily when they will be fasting from treats as an act of penance. I decided not to have them add one for any venial indiscretions. I find that I tend to focus on what they do wrong enough as it is. Trying to be more positive and acknowledge the good here!
The list of chores will be posted in several places around the house and the kids have already chosen what their first chore will be on Wednesday to earn money for the poor. (BTW we chose this route because our kids don't get allowances. If they ever were to get an allowance, I might just ask them to donate a portion of that instead.)
Here is a picture of our poor box. Shortcake chose to donate her piggy bank. It is perfectly purple, as you can see!
Oh, and if your kids are really into candles too, check out Michelle's comment below about how to do a Candlelit Stations of the Cross.