I think I would stay with discrete LEDs (eschew "strands").
It's good you have your Dad to assist, his experience will likely prove a valuable resource.
It'll require some wiring (thin gauge wire is OK
for this) for sure.
Others may see it different.
The drawing (attached) shows how I figure easiest - 2 in series with their own resistor, in parallel with all the rest, all going through the one FET, PWM-controlled, I estimate 380 mA.
(The dwg doesn't include the flexsensor, it's just the LEDs circuit.)
I see the sketch (programme) as a loop that's constantly (well, repeatedly
anyway) reading the flexsensor and adjusting the PWM output based on that...
And that could be fluid or coarse, depending on your vision
of that action.
Good "logic level MOSFETs" are STP40NF10L or IRLZ44, both available from DigiKey.http://www.digikey.com/product-detail/en/STP40NF10L/497-6741-5-ND/1039549http://www.digikey.com/product-detail/en/IRLZ44NPBF/IRLZ44NPBF-ND/811808
Maybe you have other resources available. You should buy at least a couple, in case of "mishaps".
I'll stress that you can, and should, come up with the sketch and then implement a modest test of that - while you wait for your MOSFETs to arrive.