Re:Laptop Trolley Security
It might be worth you having a look at lapsafe. There are several differenet models that you can choose depending on your needs and requirements. I did not see the demo that we got at our school but from what I have heard that you can charge the laptop in the safe and when each laptop has finished charging it automatically stops the charging that laptop. When all the laptops are completely charged it will stop drawing powers from the mains.
Well worth a look. Here is a link for you: Laptop Security | Laptop Cabinet | Laptop Trolley | Laptop Cart | LapSafe UK. It might be a bit over priced for what your looking for but great units. We are currently considering getting some of these instead of going down the rout of individual learning devices.