That's some nice glass you have yourself.
I've thought about the D610, and the D750 (which I see you have) as well. There are a couple of reasons why I'm leaning away from the 610.
1) Most of the events my wife does are low-light, high ISO. Better/faster glass will help (the 18-105 is an f/3.5-5.6), but having the expanded native ISO range helps too.
2) Newer & better AF system on the 810 and 750.
3) In theory, I think we both prefer the controls on the 810 (vs the controls on the 750 & 610). Unfortunately, camera stores in where I live just don't seem to exist anymore. We could rent both, but that's ~$300 that could otherwise go towards the purchase of the camera.