How Should I Handle a Client Asking for SEO Services?

I'm a web developer who builds and maintains websites for several small business clients. Recently, one of my clients reached out asking if I could assist with their SEO, as they're struggling to rank well on Google. I feel confident with the technical side, like improving page speed, fixing crawl errors, and setting up meta tags. However, they also want insights on competitive analysis, keyword targeting, and content effectiveness—areas I don't specialize in. I've been juggling multiple tools to manage this but it's becoming more time-consuming than the development work itself. Is there an efficient approach I can take to handle this SEO request as a solo dev? Or should I just let them know it falls outside my expertise? Honestly, I could use the extra income from this SEO work.