Windows 7: Open shared calendar on Iphone and Android device

Hello!

I've shared my Outlook(exchange) 2010 calendar with my friends in our firm. Now I want to open my shared calendar on their Iphone,Andorid devices. Using exchange activesync on Iphone and Android doesn't sync shared calendars. One solution is to create my exchange activesync account on their smartphones and disable mail syncronization but that doesn't suit me at all as they would be able to enable sync my mail on their phones. Another solution is to sync my calendar to gmail account and then add gmail account to their phones (sync calendar to outlook.com in outlook 2010 doesn't work good). Is there any other free solution for them to open my shared calendar on their smartphones, and also be able to edit it?

Thanks!