Along with our May Day celebrations we designed an altar for Mary. It was so easy to do -- I bought 2 light blue candles, let the kids sniff out their favorite candle at Wal-Mart to light (it bothered them so much that we weren't going to light the blue ones), and sent the kids out in the backyard to fill a vase with flowers (we ended up with a dandelion bouquet the first day). I had a statue on my nightstand that never quite fit there and the kids chose a pretty linen (the holy card was just laying around after being used as a bookmark.)
When the hamsters died last week, we scootched the gerbils over to make a spot for Mary. We rewrote and erased our daily memorization list on the wipe-off board and the girls wanted a world behind Mary. It was SO EASY! I guided them aesthetically and they chose most of the individual items.