Most Helpful Guy
just be normal. dont be rude, dont be overly friendly. just act like a normal person. you were together, now your not. just be casual like your fine with it.
Most Helpful Girl
Although you have 'split,' at least for now, and you have made this 'promise' to be at his sisters' dance presentation, be every bit the lady and don't give him the cold shoulder. It will draw attention, make things even more tense, and his sisters, maybe even his family, if they are Present, will pick up on your sour note as well. Talk and mingle with Him, the girls and if anyone suggests getting together for tea and crumpets after the trumpets, either graciously Bow out or go along with the flow. It's your choice, your call And----You are the one who gave them the promissory note to go.
As far as your 'things' go, be the one to just go to his house. He may be making up excuses to Not bring these to you right now, may want to see how Things may go in the future. And while you're there, just talk. See where 'Things' are still at.
On another note, wait a week or more to do this. Let everything cool down and mellow out some. Being 'by himself' for a few weeks, maybe he will have a different tune when you see him. He may just have needed some space, some alone time, and even if you both reunite, a compromise so very sweet and simple, can easily be worked out.
Keeping the lines of open communication is one of the most important aspects in any relationship. And giving one another space, room to breath, is also another Big one if you want... the Love Story to continue for as long as you both work hard to make it so in your wedded blissful lives.
Good luck. xx