I have an idea for a future proposal and was wondering if it is a good idea?

Me and my girlfriend met for the first time in a high school art cl. We started dating about two weeks later and have fallen in love since then. i have started putting money back for a ring. Around the 5 year dating mark i would love to ask her to marry me. My art teacher became a best friend over the 4 years i was in high school and i also very good friends with one of the janitors that works there. The idea i came up with was this: prior to asking her i would talk to my old teacher and the janitor and get permission to use the art room for a while on the night of our 5 year anniversary. i would ask her to dress up a little and go out to eat at a nice restaurant. Then after we were done eating, i would ask her to come with me to our old high school because my old art teacher wanted to see how college life was going. As we walked down the hall way i would stop her before we reached the door and say 'change of plans' and ask here to cover her eyes. I would then lead her into the room where the room would be set up like so: i would have tables and chairs set up in a half-moon kind of circle, around a rug, that are covered with rose petals, candles, and framed pictures of us together from the past 5 years and the lights off for a romantic setting. I would lead here to the middle and ask her to open her eyes then tell her how much i adore her and how much i would love to spend the rest of my life with her then get on one knee and propose.