Big Girl Bed

We've been letting Mia sleep in the Big Girl Bed for a week now. I'd wanted to wait until she was toilet-trained, but she's grown so much that it was getting quite difficult to lift her in and out of the crib.
She thinks the Big Girl Bed is really cool. We've had some challenges in keeping her in bed, mostly at nap time. She likes to arrange her stuffed animals on the bed and sing to them. We don't mind, as long as she doesn't get up. Jeff and I have talked about disassembling and removing the crib, but not just yet. If we did that, we couldn't say, "If you get up again, you'll have to take your nap in your crib."