hi. Can I use my turbotax account to file my 16 year old son's taxes?

you cannot use your account. doing a second return in an online account permanently and irrevocably eliminates the previous one.  you can create an account for his return. unique user ID but you can use the same e-mail address as yours 

When you use online TurboTax software you get one return per fee.

Each return needs its own account and user ID.   If you use the same account and user ID for a second return, the second one overwrites the first return and it is lost forever.  

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596

Note: If he was not 16 at the end of 2024 he will not be able to e-file; his return will need to be filed by mail.