This is an interesting project and a worthy goal. But it is troublesome for gamers to switch their system to mining and PC players may be too niche a demographic.

They ought to use Monero mining on a particular webpage on their site and ask everyone to support their cause by keeping their browser on that page when they are not using their computer so as to mine for Monero for Unicef. This is an easy way for anyone to participate... even when in the office, we can just switch on to the unicef monero mining page when we go out for lunch.

They just need to make sure that everyone is aware that their website has a monero mining addon and that all the proceeds are going to help the Syrian children.

i am sure it will be widely received this way.