Upgrading a range of Macbooks to Lion

Hello

I have a mix of Apple computers in my house running a variety of MacOS. I wonder if anyone can help me with my upgrade options.
This is a fairly complex question, sorry.

I have:

1 MacBook Pro early 2009 2.93 15" 4GB running SL
1 MacBook Air 11" 1.4 late 2010 2GB running SL
1 MacBook Air 13" 1.8 i7 mid 2011 4GB running Lion

I have a license for Lion and Lion USB drive which came with my 2011 MBA.

I would like to:

Upgrade my 2009 MBP to a SSD drive.
Find out if I can upgrade my MBP to 8GB of RAM.
Upgrade the 2009 MBP and the 2010 MBA to Lion.

Ultimately upgrade all three to ML.

What is the best way to go about this?
Do I need a new license for SL

I am comfortable with the various aspects of backing up and reinstalling s/w.
I can install the SSD

I am happy to install any new OS on to any of the computers but would prefer, at least with the 13" MBA, to simply do an upgrade.

Thank you. Again, sorry about the detailed question.

R

Thanks, the everymac tip is a useful one I didn't know and for clarifying the Lion license issue.

I was under the impression that the license covered all of my macs but I couldn't find the information anywhere.