I am getting ready to make a very long road trip in May. I have 3 ADHD kids (I'm actually joking -- sort of),

and want to keep them occupied on the trip. Thus, I think I am going to put in a DVD unit with some headrest LCD monitors. I have been looking (shopping) online. I found a set I like, but am concerned that they may not fit.
Eonon.com-E0482 2x 9.2" TFT LCD 16:9 PILLOW HEADREST MONITOR with BUILT IN SPEAKER
The specs say 160mm to 180mm (outer) between posts. So, ASSUMING that means outside to outside.. we take the measurement of 6" between posts + 1/2 the width of the posts 7/16 times 2 = 6 7/16" and convert it to mm.... I come up with 163mm. That is close-- and scary considering I am dealing with a Hong Kong company and returns would be difficult.
I am asking for others' opinions... and has anyone else used these particular headrests in their cars. Hopefully, this is doable, and I have done my math right! Please chime in...