Syncing iphones with Android phone
You have several options:

Your first option is to use a "third-party" app that works for both iPhone and Android. For example:


http://synkmonkey.me/
http://www.cozi.com/mobile-access.htm (I personally know someone that, IIRC, uses this)




Your other option is to use a shared calendar in a service such as Gmail. I personally think this solution is better. You have two options: either setup an arbitrary email account that all the managers use to sync their calendar to, such as [your-company-calendar]@gmail.com, or, you create a calendar, and if all the managers have their own Gmail accounts, make them all owners of it. This allows you to use the default, built in, calendar app on both Android and iOS devices.

To set this up (I am generalizing the steps that work with both setups):


Log in to Google and create a calendar.
If everyone has their own Gmail accounts, share it with all the managers and make everyone an owner. If not, there is no need to share the calendar.
On iPhone (I'm assuming Android would be somewhat similar) create a new email account and log on to the new centralized Gmail account - if this is the route you want to take. After logging in to the account on each device, leave calendars on, but disable email.
If you aren't doing a centralized Gmail account, make sure everyone is signed into the Gmail accounts, on their phones, that you have used to make them owners of the calendars. 


This should allow them to look up, and create events from the default calendar app on the devices.