This brings up that bad days of
ebay when there was a group that did this very same thing with great success and made a lot of money until they were caught. They would buy damage stamps then repair them, clean them and re-cancel them with a new strong mark. Thus they now sold a cheaper stamp they bough at a great return in profit.
Just mark them on the back so someone in the family doesn't mistake them for real.
Looks like you had fun and they are your stamps.