Parted Magic should do what you need. You will just need two MicroSD card readers.

When I setup my 16GB microSD card for my G1 all the instructions say to make the fat32 partition first. If this was done to your card expanding the Fat32 partition might not be an option using imaging tools.

I would setup your new card using Parted Magic then connect the card currently in your G1 and just copy everything over 1 partition at a time.