I can confirm that the man sitting on the bench outside the library DOES have the Chubby Chocobo card, I won it off him last night. You must have lost the chicobo card to the Queen first though AND have sent her to Dollet. Then you go to Dollet, get the Chicobo card back from her son and then ask her about her artist father. She will say that he made a Chubby Chocobo card and it is somewhere in Balamb Garden.

About the CC group. The earliest you can do it is once you get the garden mobile and have been summoned to see Norg. Talk to Jack. If you have won enough games in Balamb (town and/or garden) then he'll say "You've been doing pretty good with your card games - it's almost time" or something to that effect. If he just talks about the CC group the only thing it could be is not enough games, so just go win some more.

Hope that helps, and good luck with those rare cards.