Citrix VDI-in-a-Box scenario help.

We have a small office of 10 employees that for one reason or another would like to work remotely.  We are investigating rolling out a Citrix VDI-in-a-Box solution on a newly purchased server running VMWare VSphere.  I am finding the accurate answer to my licensing needs incredibly hard to find.  I wonder if the community here can answer a few very simple questions on this topic:

1. How many MS VDA licenses do I need if I am to have 10 hosted instances of Windows 7 Enterprise?  Each of these VM's will be accessed by systems at user's homes.  These home systems will have OEM editions of Window 7 on them.  There is not any form of SA on these devices.  They are simply purchased and then used to connect to the hosted VM's

10 or 20? (incredibly frustrating if I need 20 licenses for 10 hosted VM's)

2. Will this scenario allow for seamless use of Multiple monitors?  I understand that either Ultimate or Enterprise Edition must act as the VM if multiple monitors are to be utilized by the home user.  Will the VMWare hypervisor cause any issues here?

3.From what I can tell, I need to purchase a VDI-in-a-Box license + Maintenance (first year only) as well as an annual VDA license from Microsoft (~$130/Year). My ongoing costs after 1st year should be only the VDA license correct?

I think that covers my most pressing questions so far.  Your help is appreciated as always.