I have the Mamiya 7, and love it, but it has its limitations expecially with kids. Inevitably, I have to pick my three year old up, and I'm always bonking him on the head with the lens! Also, with only ten frames, you have to change film a lot, and it's a cumbersome process. I still love the results I get with it, but it's not quite as fluid to use as a 35mm rangefinder. I have an older Leica without a meter, and I don't find speed an issue. I just take a meter reading with a hend held meter, and unless the light changes, I can just shoot away! I almost bought the Bessa, but found a reasonably good deal on the Leica, and went for it. Whichever rangefinder you settle on, you'll love how they work, especially photographing your kids! Good luck!