If your worried about losing potential players you can always make the link nearly invisible to players (instead of having text link to it with an image that nobody will consider clicking). Don’t use invisible text or you’ll get banned. Most others will say this is deceptive but it works just like a text link and your running the same risk.
As for linking out – It’s hard to say if it will or will not help others. Some websites may jump 30 or 40 places, but still receive no traffic. Some might only jump 1 place and notice a big boost in rankings.
Even if they do not get higher rankings straight away, they might get another PR point which will in effect give them an opportunity to get other quality links.