That's an intuitive theory, but inflation doesn't really have that much to do with the quantity of money, because the value of money is almost entirely based on what you can buy with it. Price inflation happens when the aggregate demand (the sum of all the spending over a certain period) outstrips the amount of goods and services produced (or held in inventory) in the economy. Yes, adding more money can increase aggregate demand, but it is also saved or invested in productive ventures that mean more goods or services are produced.

If it was simply a fact of more money == inflation, we'd be screwed since the money supply is almost constantly growing through bank lending.

At the end of the day, all spending carries inflation risk (since all spending adds to aggregate demand). This equally applies to money saved earlier, new money created in the banking system, or new money created by the Government (say, QE). It's at the time of spending that's the risk, not the time of creation.

The limits of Government money creation therefore have more to do with the productive capacity of the economy.