This year our family will keep Lent very simple. I posted more ideas on this post last year with lots of resources for the whole family.
On Ash Wednesday we're going to say farewell to the Alleluia. You can read about this old custom here.
I learned about this from Dawn's post last year. I bought wooden letters and a paperboard box and spray painted them gold. Then the kids glued some glittery flowers on them. We put the letters in the box and put the box away until Easter morning, when we will open it to reveal the Alleluia, which we will display during the fifty days of Easter.
We're also going to make the Crown of Thorns. As the children are caught being good, carrying out a work of mercy, or other good works they are allowed to pull a thorn out of Jesus' crown.
Another way to help the children focus on Lent is to meditate on the 14 Stations of the Cross.
I came up with this craft last year after finding these printable images of the Stations on the 4 Real Learning forum.
Here is a sample of the first station. 
I glued the pictures on small votive candles I found at the craft store. In the evening we light all 14 candles, read about each station and blow out the candle. Finally, when we get to the last station the room is completely dark.
We're also going to cover our crucifixes with purple cloth and take it off on Easter morning. .
May your family have a holy and blessed Lent.