I can't see it making a difference at all. I've spent time in India on my own throughout my twenties, which included everything you'd expect - things like travelling on trains alone, eating alone, shopping, walking around the streets, etc. I even ended up on a camel trek in the middle of the desert alone when my friend fell ill and had to go back to the hotel. This latter one may not have been super wise in retrospect, but we'd been with the guy for a couple of days already, I felt secure, and everything went smoothly. I've never had problems doing any of the other things, either. I'd say that your being older will, if anything, be an advantage, as it means that you've got the experience to know how to handle yourself. I found that if I dressed conservatively, was sensible, and trusted my instincts, things went well.
Also, as I'm sure you know, one of the worst things is to go and not trust anybody. I went to Varanasi to visit a male Indian friend of mine. We were sitting on the side of the street, chatting, and three very lost, very hot and bothered looking English boys with great big backpacks walked along the street and stopped near us. We asked them if they were all right, and they said they were looking for a hotel. My friend tried to tell them that the one opposite where we were sitting would be exactly what they were looking for, but they immediately brushed him off, assuming, I imagine, that he worked for some hotel or other, and possibly having read too many guides telling you to be cautious. It's interesting trying to imagine what would happen if this happened the other way around - if people came to our home countries and we tried to help them and they assumed we were trying to scam them! I think that being older and having your travel experience will just make your trip richer. You'll be able to relax more, and know better when situations feel not right, so that you can relax more the rest of the time, and get a lot out of your travelling. It's very possible that people will treat you with more respect, as well. I'm very excited for you. When and where will you be going?
(Incidentally, I found that wearing a shalwar kameez was indeed a very good way of making sure that you could make friends. Wearing the shalwar suit goes down very well, everywhere you go.)