I have a Mac and iphone and have bought many apps, games and music for my two children. They are now older and have their own iDevices and want to view, watch, play and listen to the same things they used to on my Mac or iPhone on their own devices.
Is there any way I can share my content using iTunes (using two or three different Apple ID's throught iTunes) using just one Mac?
Not immediately. In an attempt at anti-piracy, iTunes has locked down the transferr of purchased content for 90 days from the point of activation in Home Shairing. You may be able to transfer the files individually, then plug your apple ID into his computer and try it that way, but that is a shot in the dark for me.