i thought it was my son and me, i was told that the sentance should work with the second person removed, so saying "i bought a nook for i" would make no sense
This is absolutely correct. If you are ever unsure whether "me" or "I" should be used, you can either remove all other pronouns except the "me" or "I", or you can substitute "we" or "us" and see which is correct. We = I, us = me.