That will work, but consider plate heat exchangers instead of buffer tank on the cold side. That will give you a significant COP boost. Also, run in parallel to the heat pumps so that you don't get one that receives cold brine.
As mentioned above, there is no gain in using many small compressors. The same goes for pumps. Get a pump that can maintain a constant pressure trough variable speed (one for the whole house), and then use magnetic valves to turn on and off the waterflow. In a concrete floor you could use cycle periods of an hour or so, in a wooden floor it should be some minutes. You can also get variable valves that has a continuous flow adjustment, but those are expensive.
Layering them with about a meter between (3 feet) will give you possibility to grab more energy in a short period, but after some weeks of running it will be almost as having one, as both of them will grab heat from way more than a meter away, as much as 30 meters after 10 years, and then they will only be able to grab from one side each, like if it was only one loop. If possible, you would get more energy per meter tube if they where spaced further from eachother, which gives a better cost-performance for the tube. Then there is the price of digging the trenches to consider. With only a meter between them though, you should consider them as one in a long term perspective.
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