How to minimise trace fracturing in PCB design - multiple thin traces or one thick?
Tricks we have used with some success:
Make your feedthru holes big enough to insert a small piece of bus wire and solder top and bottom.  Also solder top and bottom on your sensors if possible.  We have seen lots of breakage between traces and the plated through holes and this is pretty effective, especially if you use 2-sided boards.  Multi-layer boards are prone to cracking between trace and plating on the plated through hole, so stick with two-sided if you can.  

If you must use multi-layer, be sure and watch the heat on your joints.  Overheating can stress the joint because the board material expands at a different rate than the copper.  The idea is to prevent cracking at the outset.

Trim component leads before you solder; Trimming them afterwards can stress and start a crack which will propagate.

No sharp corners on the traces.  Cracking often begins on the corner where a trace runs into a pad outer radius.  Fan out the trace to where it matches the pad tangentially.

For long parts like through hole resistors, mount them parallel to the expected flexure so that the leads are not getting stretched and compressed.

If you have leaded parts that mount flush, leave some space so that they are not sitting directly on the board.

Of course, you are probably already mounting your heaviest parts nearest to the mounting holes where they have the most support.

Good luck!