For MacBooks, MacBook Pros and MacBook Airs it would be best if they were unibody models 2010 or newer and for iPads the best is 6th generation of newer. Otherwise, they are likely unable to run a viable version of the MacOS to be of much use. Email me if you have questions.
Please read this article and if you feel led to help or donate, contact me on my contact page or email me so we can connect. It's for a great cause - I've witnessed it through my own eyes... our 11 yr old son has Leukemia and I go with him to cancer clinic and my wife takes him for hospital stays and the positives of having available tech equipment like this to distract these kids is priceless. Please donate and/or spread the word... thank you!