Here is a great link on removing and potting up keiki's from phals -
http://www.easyorchids.co.uk/site/content/view/30/71/. What you are ready to do will probably work fine. You will find that many types of pots are used and many types and mixes of media are used - your growing conditions and how you take care of them will dictate what is best for you personally. I would tend to plant the keiki in something that will stay a little moister than large bark - either smaller bark, my current favorite, coconut pith with a little perlite and charcoal, a combo of bark and sphag, or a host of other options. The clay pot will obviously dry out more frequently and require watering more often - both types will work. Some even like the semi-translucent white plastic pots because you can see the moisture inside and the conditions of the roots as the plant matures and grows. On phals it is better to underpot (size-wise) than to overpot. Good luck! mike