DD went into her toddler bed on her 2nd birthday and she wears a sleeping bag with legs in case she needs to get up and walk. We leave her door ajar but we always have as we don't have a monitor. She has only got herself out of bed twice in 6 months - the rest of the time she will call out to me to come and get her, even in the mornings!

I think if you normally close the door then keep doing what you normally would as that is what she is used to.