question about pg_dump -a

I have a database which I create using dia and tedia2sql.

I developed another version with more tables, without changing anything
that was already present in the first version.

Now I want to copy the data from one database to another, so I thought
about pg_dump -a, assuming that since there is no change in the
structure and I can freely and and reload the information.

My problem is that when I reload the data into the new database, I have
several error about foreign keys violation. For what I've been able to
understand, it seems to be a problem of loading order and tables
referring to others are loaded earlier than those.

Is there a way to export tables in order, so that dependencies are
always met? reading the manpage of pg_dump I found the -Fc flag, but I
haven't understood if it is good for me and how it works. Or is there a
way to relax constraints while loading data?