You can absolutely have PlayCanvas running alongside a Node app, I’ve been working with having the engine running on the server-side for several months now, and it runs very well.
What I did to run it was just “emulating” a fake browser inside the server app, so every document call etc calls and empty function.
I did have CPU consumption problems with a project that I still have to rework, but I do think that was merely my fault as an inexperienced JS programmer.
It’s very late right now but I might be able to share with you the node module I did to be able to run the engine on a node app, and also a tiny example on how to do so. Tho it’s a very hacky situation, so keep that in mind. I’m not a brilliant programmer either so I’m pretty sure everything can be done in better ways 
Currently have a very big project under development which is going to use this solution.
If you have skype, add me up; My name there is midgardh
Also, I’m glad that you decided to use PlayCanvas. It is a great engine and it’s made me recover inspiration for future web projects, I was highly frustrated with Unity, but this one is a life saver - also the live collaboration tools are amazing, if I ever manage to build a somewhat small team for my studio these tools will speed up the development process a lot.
I’ve also gone back to doing games with Unity as part of contract jobs aaand man, it does frustrate me even more than back then.
Edit:
Some insight can be found in this thread (which I did read when I was planning to wrap PlayCanvas inside node): Engine - headless