18 Y/O having a web development interview. How to look professional?

So I've been studying web dev by my own since I was a child and now at 18 I have some pretty solid experience and skills. Since I've put a lot of effort on my linkedIn profile, I've been receiving a lot of job offers lately. Most of the recruiters don't know that I'm 18 or don't even ask my age.

I've got a presential interview for tomorrow and I'm afraid that when I reveal my age, they might take it as a deal breaker(I look quite young so they're probably gonna ask it).

So, what can I do to make them feel like despite my age I'm a good long-term investment for the company?

Also any other web-dev interview advice would be appreciated! thanks.

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official