I would definitely use both. Especially coming in to the hotter months bubba start to sweat and you never know when they are going to fil their bed with vomit. I have the matress protector on the mattress and then the woolen underlay over the top of the protector as it is more comfortable for bubby.
I can't believe your little bubba is going to be here any day now!! So exciting!! Wishing you all the best for your upcoming birth.