I think you'll probably be fine getting in. But, regardless, I wouldn't hide the grades since even if they didn't find out, you definitely want to feel like you deserve to be there and that you weren't accepted on information that didn't represent you as a whole. I think that could affect your performance later on in the program. Just apply with all the information they ask for - truthfully and in whole - and then if it's supposed to happen, it will.
I think you do need to disclose all grades, if they ask for them. Call and ask anonymously. If you are required to disclose and you don't, you will probably be asked what you are doing with your time now (the time you are completing your post-bac) and you will be either forced to lie to cover up or end up disclosing anyway. It's a lose lose situation if you dont.
On another note. I think you really need to look into your focus and motives for becoming a doctor. This post-bac year is a sink or swimming kind of deal, and you (sorry to be blunt) are barely treading water. SMP is very expensive and I doubt anyone can afford not doing well. YOU MUST GET A's. Settle for nothing less. Before enrolling look inside yourself and ask am I prepared to dedicate the rest of my life toward's this?