Have been using various Kobo's for years with KOReader now, it's basically as simple as copying files on the device to install it. There is no need to jailbreak it; it's an open device. Also, I haven't heard any mention of covert update to worry about. So yes, I would absolutely recommend a Kobo for your use case.
A few months ago, I attempted to do install KOReader on a kindle, and the experience is definitely not for the faint of heart. Plus, I can't use the wireless capabilities for the reason you mentioned. It was (one) of the reason I wanted to install KOReader in the first place, but live and learn.