I have a vista PC, a win 7 PC, and an emac all connected to a cisco e3000 router. Need an all in one printer to serve all. Also have an iPad which now has a print function through wi-fi.

Since I am not a geek, need easy installation, low cost operation. This is normally a low volume application for printing and copying, about 150 / mo. Ooccasionally the volume spurts because of a large copying need.

What is recommended?

Well researching printers is your best option. Most big names (if not all) inlclude drivers that support 7 and Mac (including IPAD)

At work I have a Ricoh 821-DN that works great with XP, 7, and OS X but that costs about $10,000 and does like 40ppm in Color, many finishing options, etc... so I'm thinking that's too much printer for you for only doing 150 rips per month;)

Research and you will discover what printers have what you need. Try googleing it!
What price range are looking toward? I can recommend an awesome vendor if you're near me :D