A Hypothetical Trade

My father gave my 7 year old son $9.50 in silver quarters to bring to the next coin show we go to(it actually started out as $10, but he let my son pull 2 UNC quarters for his own collection). He told my son to see if he could bargain an exchange for three common date coins in AU-UNC condition:

1) a Morgan dollar

2) a Peace dollar

3) a walker half

Any profit my son gets to keep. My son likes the prospect because he loves the bargaining process. My question is, are these goals realistic? I haven't been to a coin show in a while, but I figure that I could easily land these three coins for under $80 total. Even at 10x face, my son would still be able to pick up a Franklin for the set he is working on.

For the record, my father told my son to do the best he can. He really just wants my son to have fun and learn a little about the bargaining process.