I am aware of only 2 official combined programs (not including the pediatric/psychiatry/C&A combined residencies). They are Yale and UMass. The Yale program is really a research track. I believe it is fairly competitive and you have to have a background in research that demonstrates your commitment. The UMass program is also competitive b/c of its uniqueness and the fact that they only take 2 people (at least that was the case when I applied).
However, there are a lot of programs that have an unofficial policy that if you decide to do the child fellowship, you're virtually guaranteed to have a spot as long as you're in good standing. The programs that I know who offer this are Pitt, Brown, Indiana?, and Penn State. There are likely a lot more then this. The best thing you can do is to contact the programs and ask them directly.
