West Sussex to Hawick- route suggestions?

[CNNCHI]

Couldn't find any recent threads discussing this, so:

Due to drive from West Sussex to Hawick, Scottish Borders at the end of February- first long drive with a 6 month old. Totally flexible on departure time, but need to be in Hawick around 3pm on 22nd February. The wife doesn't drive, so it's all up to me. Not done much long distance driving to be honest, so I was planning to take it easy and take two days to do the journey in case my son decides to be a nightmare.

Looking for suggestions on a route, where you would stop overnight, and what time to leave to best avoid traffic. Happy to pay the M6 toll if it means a calmer route. All advice welcome.

Thanks in advance, CNN

[CNNCHI]

Thanks for all the answers chaps, much appreciated. Setting off now- the plan is a stop in London to visit family for lunch, then A1 all the way to Newcastle, A696, A68.