If the IDS for 64bit will run on the same box of the 32bits, you don't need export the database.
Just install on differ path, copy onconfig/sqlhosts, stop 32bits and start the instance on 64bits...
This works very well and fast! I already do that.. .but i migrate from IDS 7.31 32bits to 7.31 64bits.
More information: read the Migration Guide...
About 4GL, be careful!!!! if you use Shared memory (onshmipc) the client MUST be 64bits too!! if you won't recompile your 4gl or you don't have the 4GL 64bits , you can change the connection to PIPE Stream (onipcstr) or TCP/IP (onsoctcp) without recompile your programs....