Add a VM network to the vSwitch that has the pNIC on it. This will communicate out to the rest of your LAN.
For private LANs, seen only by VM's on that host, simply create a vSwitch, create the VM port groups and just don't assign a pNIC to the vSwitch. Very easy to do and no need to over-complicate things. If you want to have different IP addresses for those internal VM networks, than what they self-assign, then you'll need to configure them to do so. You have options there. You could try setting VLAN ID's on those port groups. Bring a router virtual appliance online and assign the different internal network adapters to it, giving different IP address ranges to them. As I mentioned, you have options. You could even just use static IP addresses for those network connections, eliminating the need for additional configurations.
If you do make the internal only port groups/networks, I would go with the VMXNET3 adapter in the VM's you're going to put onto those network connections. For internal network traffic, that should give you the best performance. I've seen cases (with 4.x) where you would get 10Gb speeds between VM's that way. Or that's how the OS/adapter translated the speeds in the VM.
Curious to know why you're only using one pNIC connection on an ESX/ESXi host... What are you going to be using the other two networks for? IMO, the bare minimum (with fiber attached storage) is six pNIC connections. Two for management, two for vMotion and two for VM traffic. Add iSCSI storage and you'll want at least another pair of connections there.
