The CNS role is ill defined at best. We operate at the whim of our individual state boards. lol
I am an adult health and peds CNS who is also an APRN. You might want to look at the Consensus Model;
American Association of Colleges of Nursing | APRN Consensus Process
as it may change how you think of your future. Right now, you want to stay at the bedside. However, in the future, you might want to have more autonomy, ability to prescribe, care for pts, etc.. I pigeon-holed myself into the CNS role without thinking it thru. I am just fortunate that I live in a state where CNS is an APN.
Personally, I think going the MSN|NP route with perhaps some education courses thrown in, would fit you better down the road and give you more options. You will probably end up working another 40 years or so, so by choosing the correct education route, you open the door to more opportunities.
That said, you will also find that I truly miss my bedside ER role very much. My first year as an APN was extremely traumatic forr me professionally and colors everything that I now do, even 7 years later.
Have you talked with another CNS (maybe one not so jaded as myself? lol