I have to warn you ... be very very careful about your expectations when it comes to getting a PhD. It defies logic when one considers the simultaneous push to graduate more PhD students when there are very very few faculty jobs available. Are you okay if you get a PhD but then never get a chance to use it in your work? Think hard about this ...
Doing it when you are older doesn't stack the deck against you in my opinion. I've known a few older PhD students in CS and I think they have some advantages over the under-30 bunch. Specifically, I've heard of some under 30 PhDs sometimes being said to "look" non-professorial. I guess some people expect professors and researchers to look a certain way (I think those people are idiots btw).