I would be tempted to create a primary, larger table, into which you will be placing your three existing tables. Make sure you make the primary table set not to adjust based on the contents.

You can then center the middle table within the middle table of the primary table (tables within the table), I think.

We ended up doing something like this, with a three column table across a large sheet of ledger paper. The left-most cell of that table houses a smaller table with lots of very intricate cells. The middle cell contains running text, and the third usually contains a photo and a photo caption.

Best of luck,

Ann