The good news is that, even if your undergrad GPA is low, you're fresh out of school, so you have a lot of time to really make an impact in your career before applying to b-school. If you put together a stellar resume over the next couple of years, your undergrad grades will be less of a factor.
When were you thinking of applying? I don't believe that part-time programs take younger people than full-time counterparts. In fact, I think their students tend to be a bit older than their full-time counterparts (although I don't think being older is a requirement). Anyway, you probably should wait a few years, either way.
Some programs (e.g., Kellogg) do let people transfer from part-time to full-time, but it's not easy at all. I know a couple of people who did it, and it was harder to make the transfer than it was for them to get into the part-time program to begin with. So, I wouldn't consider that to be a foolproof plan. What if you get into a part-time program, find that you hate burning the candle at both ends (which ends up happening to a lot of part-timers), and then can't transfer?
Is that the main reason why you're interested in a part-time program, because you think it would be easier to get into? That is often the case (on a pure numbers basis), but you'll naturally need to come up with more compelling reasons than that if you want to impress adcomms.
I don't mean to sound harsh. The main takeaway is that you still have a lot of time. If I were you, I'd focus on getting 3-5 years of killer experience and then applying, whether you're thinking of a part-time or a full-time program by that time.
Scott