Well let's think about this issue again. I beg you pardon but I still believe this is going to be an issue. Let's assume I have deposited 12 coins and have gotten 100 bitnotes 0.1BTC each. Let's assume 0.1BTC is valued $10 fictitiously. Now let's assume we need to pay for our dinner which costs $27.99. On top of that let's assume that the Bitcoin price will be fluctuating like it is now and the price constantly changes every other couple of minutes or so. We don't have to tip the waiter and want to pay the exact sum it's on our tab. How would we manage to assemble the exact same amount with our bitnotes without going short or paying more? Mind you the Bitcoin price is changing as we are talking to the waiter and fiddling with our bitnotes.
I think you failed to assume something here. First, the assumption here is that by the time we have bitcoin notes and coins (physical coins like dimes, quarters, etc), there has been great adoption of the Bitcoin already. If there has not yet been a great adoption then you would not likely be paying bitcoins at a restaurant. Second, if there has been great adoption, then the prices for sure has stabilized already or, (pushing our luck here) there is no other currency already but bitcoin itself.
If you assume that there are no other currency but bitcoin, then you don't even have to convert your money into dollars. But if there are still other currency beside bitcoin, like the USD, then you can convert it similar to having Yen, Euro, Dong, Etc. The prices doesn't fluctuate that much hence solving the problem.