Consider just using Screen Sharing from the Mac with a larger monitor to the other Mac. It is rather reliable.
Besides using Screen Sharing to control a remote Mac, I also use it from the 32" 4K monitor I have on my work Mac to my personal 15" Macbook Pro that I take to and from work with me. When at work, I connect my 15" Macbook Pro to the network, and the existing Screen Sharing session on my work Mac re-connects to my 15" Macbook Pro and I can access either Mac from the same keyboard, Magic Trackpad 2 device. I just select the Screen Sharing window when I want to do things on my 15" Macbook Pro.
Another trick if you have a monitor attached to the other Mac is to use a utility such as Synergy, SynergyKM, ShareMouse, access, .... which allow you to move your mouse off the edge of one screen and it magically appears on the screen of the other Mac, plus all your keyboard traffic is not directed to the other Mac as well.