My two port power supply looks similar to the Sweex Brandon92 is showing except mine had US plugs (although it is rated 100-240VAC 50-60Hz) so with a plug adapter it will work anywhere. It has not Ground pin.
I guess I am missing the concern here. If either socket goes down, it does not matter to me that the other is also down. This is because without power to my water meter reed switch, there is nothing I can measure and without power to the Raspberry Pi, the ticking of the reed switch will go unrecorded. Both are necessary for the system to work.
As a result of everyone's help, (thank you for your insights) I see the point of separating the power used for the raspberry pi and the 24vac detection circuit from the power used for the reed switch at the end of a 30m cable. This will help protect the raspberry pi (a 35USD item).
I'm not too worried about protecting the A3700 as they are not too expensive and I can easily replace one in the socket it it goes bad. The A3700 is an opto-coupler so it should protect the low voltage dc side from the higher voltage AC side if there are spikes.
We have discussed a lot of concerns about connection to ground but the two port USB power supply has no ground pin anyway and I'm not sure how having one would affect (either for good or harm) the 5vdc circuit.
Even the Sweex Brandon92 shows us has no ground. BTW, looking at the picture of the "Official" RPI powersupply, the US plugs have no grounds either and for the UK/Hong Kong plug, the pin that goes into the socket hole for ground looks like it is a non-conductor there for the purpose of unlocking the powered holes in the socket.
I think I am missing something here.
PS. Went skiing in Park City, Utah for a week (Near Salt Lake City). We had great weather except for a worrisome storm while driving the 13 hours to get there. I've been away from my project. I'm back now and when the winter rains here calm down a little, I'll go out and start digging to install the first water meter.