I think I've just ruled out the Honda 2 hp - it doesn't have reverse. It has a swivel mechanism and has to be turned around to go in reverse. I imagine for someone with experience that isn't a big deal, but for me, the difficulty of docking doesn't need the added issue of swinging the motor around!
I had a similar motor when I was 12 years old (no neutral or reverse, but a 360 degree swivel with a handle that flipped backwards) and I had no problem figuring it out at that age. That motor had no clutch at all - the prop was always spinning, and it still worked fine. I think (but you should verify) that the Honda has a centrifugal clutch that disengages the prop at low RPM, which is a little more user friendly than the one I had.
If you feel more confident with 4 hp and really want a reverse gear, that's fine. I certainly don't want to push you into getting a motor that you might be unhappy with.
However, let me make a couple of final points. First, I wasn't suggesting that you should go motorless with paddles. With small kids on the boat you need a motor. I just meant to imply that 2 hp is much more thrust than you would get with paddles, so 2 hp should be adequate for this boat. Also, someone else here already pointed out that he could get 5 knots out of a 1.5 hp motor on his former Flying Scot, more evidence that 2 hp may be all you need.
Finally, one last consideration. I have not owned any of these small motors (as you know, I have a 15 hp Honda on my boat), so I have no personal knowledge of their reliability. I expect Tohatsu or Honda to be low maintenance. But the Honda has air cooling and no reverse, eliminating the water pump/impeller and shift mechanism, which are two maintenance items. Since you had asked about reliability and maintenance, the simplicity of Honda's design would be a plus.
In the end you need to get what you're comfortable with. You'll get no complaints from me if you go bigger than 2 hp. When I was shopping for boats I frustrated several people because I didn't follow their advice, but I'm happy I made the decisions that I made. As you're undoubtedly experiencing now, when you get so much conflicting advice it's impossible to follow it all. So good luck with whatever you do.
EDIT: One last thing. I have an inflatable rowing dinghy that I've never used (see my avatar pic). If I ever start using it regularly enough to need a motor, I'd get the Honda 2 hp in a heartbeat.