Introducing myself to researchers from my dream school I am applying to a PhD program in a few weeks, and I am also going to give a presentation at an upcoming international academic conference. I heard that a group of researchers from my dream school is also going to present their work at the conference, and at least one of the researchers might be a member of the admissions panel. I would like to introduce myself to them, but I don't want them to think that I am trying to win their favor just to increase my chances of getting accepted.

I recently had an informal Skype meeting with a potential PhD advisor, and she agreed to supervise my research if I get officially accepted. She does not belong to the research group and she is probably not attending the conference. 

Could you give me some advice on how to talk to them in an ethical and appropriate way? Would it be fine to let them know that one professor is already willing to accept me to their program? (The conference will take place before the deadline of the application.)

[EDIT]
Thank you @ReinstateMonica for your answer. As (s)he pointed out, there was inconsistency in what I wrote. My potential advisor is willing to take me in, but she is not the one who will make the final admission decision. (My understanding is that my application will be assessed by her and one or more other professors.)
That is called networking and it is about getting to know people and people getting to know you. It will increase your chances and that's exactly the point.

There is absolutely nothing wrong, immoral, or illegal with it, by the way, it is a necessary skill for all professional careers. Conferences usually have intermissions for that exact purpose, with snacks, refreshments, etc. 

The "standard" way of doing that would be to walk over, politely introduce yourself (don't go all formal), from which school you are and briefly, very briefly, what you are working on. Don't be pushy, don't force the conversation. It is easier if a common acquaintance introduces you (for instance, another researcher that knows you and them). Bonus points if you are familiar with their work/field.

It's easier after they see your presentation, but that's not entirely necessary. The most 'busy' researchers don't usually attend the whole conference, so don't waste chances.

More importantly: forget dream, don't be starstruck. They are just people, it is a school, just like countless others. Something I saw people do wrong: don't get stuck talking shop, especially if you have more time (as in the formal dinner some conferences have). Again, professors/researchers are people, they do more with their lives than just research and certainly have some other interests.