Established Schedule C under SSN. Creating an EIN for side work. Do I need to do a second Schedule C for that or can it all be under one?

For 10 years I've worked as a freelancer/contractor for the same law firm & nothing else. Always used my SSN for Schedule C. Now I want to create an EIN to use for some infrequent side jobs. Do i have to create a second Schedule C for that EIN & keep using my SSN for the established long-term work -OR- can i change my current Schedule C from using my SSN to using the new EIN and roll it all in under the same Schedule C??? I don't want to mess with my long-term historical use of SSN work in fear of triggering an audit. Which would be the safest route (2 schdule c's or 1)???