Sonar 4 or 6 or 8 with Pentium M?

I use Sonar 7 but I would think 8.5 will work too, No problem at all. The only thing that kills a computer is adding the VST's and soft synths. Recording/ playback of straight audio  is not hard work for even older computers.  I have recorded 12 tracks audio all night long on a similar computer. Recording MIDI without using a soft synth to audition it is even less work for a computer. What I have done in your situation is record both the analog and MIDI output from the drums ( or keyboard)
This gives you the ability to playback what you have recorded right away without fuss. Back at the studio on a more powerfull DAW you go at it with adding soft synths and EFX. And do all your editing.
Just a tip.
As to keep everything easy to move from one computer to another.
On the remote laptop
Make a folder with the project title and with DATE.
Put all the CWP and audio files in there.
Make sure the pathways are set to only to that folder for your audio.
Then you only need to copy that folder to a USB drive.