upgrading and pg_restore versions

Dear Postgres gurus,

I come seeking advice on upgrading my 8.1.2 databases to 8.2. My
environment in a nutshell: I have a master database on one server that
is used to process large amounts of data. This data is replicated daily
to several destination databases, each on a separate server. There are
so many destinations that I fear I won't be able to upgrade them all in
one evening.

Does anyone know if it would be safe to upgrade a subset of the
databases per night? I am concerned with version mismatches between dmp
files, pg_restore, and destination database versions. Should the
pg_restore still work ok? And if that is ok, should the master database
be upgraded in any particular order (before or after the destinations)?

I would greatly appreciate any advice that can be offered.

Thanks!
Mark