I agree with the Gro-clock suggestion, we have one for DD & it has really helped with understanding WU time etc.
I've not personally used W2S with either of my 2 LO's as toddlers but I know some Mum's have used it successfully but they do it earlier on in the night, so around midnight or so, when their LO is still in a deeper sleep. The risk to doing it later in the early hours is that they are in a lighter sleep & therefore are more likely to be fully woken & then won't go back to sleep.