Low power gaming pc build help.

[bigmeanie]

Budget (including currency): I need to build 4 of them, so dollars count.

Country: USA

Games, programs or workloads that it will be used for: Modest gaming and school work. 

Other details My sister is going through a D and is moving in with me (trust me, I'm real happy about this) and her and her kids both have some problems, so I can't just go with laptops or anything that can be tossed in anger or sold easily. And power budget wise I'm going to have maybe 100 watts per machine at max. Lower is better as these systems will be running mostly off of solar. I'm making due with some very less than ideal circumstances, but her kids are decent kids and I would like to make sure they have something that can at least do some gaming. 

 

It don't need to be pretty, it just needs to work.