I don't think age has a thing to do with it. It is all dependent on the type of person that you are. If you love the Vegas dance, drink, and gamble all night; Celebrity might not be for you.
I'm 39 and my wife is a tad older. We have sailed Celebrity since 1999 and our eighth Celebrity cruise is in 45-days. There is lots to do and you can have a great time. You just have to understand who Celebrity is geared toward.
Celebrity is geared towards a toned down crowd. Yes we can be crazy and drink and gamble, but its more eligant than Carnival or RCCL. I personally think you will have a great time.
My advice is you have to try it to know what you think of Celebrity. I can tell you what I think but my tastes and likes may be vastly different than yours. I have tried the major lines (Celebrity, RCCL, Carnival, HAL, Princess, NCL) and I have my opinion on each and which ones I like and don't like.
Again, you have to try it to know for sure. It's a cruise, how could it be bad?