Setting up lvm with HDD and SSD
Solution 1:
I think your plan is OK but while you are at it, why don't you put the /var on a Logical Volume too instead of a separate partiton on your new drive? I find lvm a lot more flexible than regular partitions. My main machine is all using lvm, including / without any problem and very quick to resize/reconfigure Logical Volumes.
To use your current HD with lvm, you'll need to empty and format it. One way to do that is to put the new drive as a device in the Volume Group, move your current home to it, format the current HD and add it to the VG.