the company I used to buy materials from, Increte, makes a thinset product for stamping existing concrete. that would probably be the cheapest solution to your problem.. I believe they lay down 1/4" to 3/8" thick and stamp it just like concrete. you probably won't notice any difference from concrete after stamped and colored
http://www.increte.com/vProduct.aspx?ID=4
a pool I did last summer had someone pour and stamp his deck. I just hope no would thinks I had anything to do with the crappy patchy colored, rocks showing thru and cracks the next day $11,000 concrete job. I can't believe they actuially charged for and got full payment for such poor quaility amatuer work.