I was bullied relentlessly throughout secondary school, both physically, verbally and mentally, by certain individuals and it had such an impact that I left school at 16 rather than carry on through the 6th form as I couldn't cope with it any more. To be fair and balanced, I always knew I didn't want to go to University even though I was more than capable of doing so but I always felt that my choices were heavily influenced by the bullies and taken more through desperation and unhappiness than of my own volition. Do I regret it? No, I went on to live a happy life and have a good career in something I enjoyed immensely.
I was contacted a few years ago by one of the worst bullies via Facebook, who sent a very chatty message and appeared to have totally forgotten than they made my life a misery for so many years. I did reply, something along the lines of, "Yes I remember you very well" and blocked her, and that was it.
I think you are being unrealistic in thinking that your childhood bully will acknowledge what happened long ago, or admit to it. If you expect an apology you are setting yourself up for disappointment, more bitterness and a stirring up of emotions that you do not need. Either take the higher ground and ignore them/treat them as though you vaguely remember them or just don't attend and save yourself all the re-kindling memories that you really need to move on from for your own peace of mind.