I have a lot of cels too and I can never decide
what to bring. I usually try to condense the ones
I think most people would like (plus a few of my
personal favorites) into 2-3 books. I avoid
bringing the larger ones since I'm afraid they
would be more likely to be damaged.

As for trying to guess which one people will like,
that can be very hard. Everyone's tastes vary so
much. You can try asking here if anyone is going
to the same convention and then what would they
like to see from your gallery.