I believe that you can use boto with the current release of App Engine (and possibly AEP to help, although it may not be necessary for your specific task of starting an instance and getting its public domain name). This post provides a good overview of “lessons learned,” while it all works. (Sorry, no personal experience - my random game with AWS was made from my laptop, disconnected from my more intensive use of GAE ;-).
If this does not work for you or does not meet your needs, perhaps you could give us information about what you tried, how it failed, and what behavior you are looking for ...?