By the way, I just googled the restaurant and thought menu looked quite interesting, and wine list has nice variety (way more old World wines than most CA places) and fair pricing. Might indeed suggest this next time we are in CA.
And since you framed the questions as ethics rather than marketing, it's always interesting to take anonymity out of the equation for ethical questions. So here's another argument for a disclaimer. Say I had asked here for a recommendation for a Sacramento restaurant. You had responded Pearl On the River. So you could either mention relationship or not. And I could like meal or not (I've never heard of a restaurant that everyone liked). So four possible combinations:
1) you told me owner was a neighbor, and I liked restaurant. Great!
2) you told me owner was a neighbor, and I didn't like restaurant. Shrug, tastes differ, places have off nights, etc. No biggie, wouldn't give a second thought.
3) you didn't tell me owner was a neighbor, and I liked restaurant. Great!
4) you didn't tell me owner was a neighbor, and I didn't like restaurant. If I found out later owner was your friend, on some subconscious level I might
wonder if I had been conned. Obviously that wouldn't have been your motive for suggesting (the fact that you asked re ethics reveals you don't have ulterior motives) but it breeds questions.
When in doubt, disclose!