Plenty of people go to uni at your age, I'm about to go into my 3rd year and have three friends who are 23/24 so will be around 25 when they graduate. It's relatively common and since you're in a social group with all the other students, most people don't really note who's older or younger - especially if you're in your twenties. You're also definitely not too old for that career, you can reinvent yourself and try something new career-wise at any point in your life. If this is what you want then go for it!! Also, in the grand scheme of things you are still young. And better to try something you want to do than to miss out and regret that because of other people's opinions.