Your plan sounds fine.
I think it may be a little more than three miles to walk around the road.
If it were I, I'd walk down the track to the WHHR station and catch their train to their museum, have a look around then walk to my digs for the night.
FYI The WHHR and the WHR stations have great food. The WHR station has a pub too with an ancient steam loco in the bar!
Additionally, one can walk across the causeway called the "Cob" to the original from the 1860's, much expanded "Boston Lodge" works where the locos of both railways are overhauled.
You need to ask permission to look around, in my experience some access will be granted.
Look out for the newly arrived Chinese C2 0-8-0 loco in one of the sheds. It is to be overhauled and re-gauged, hopefully for operation on the WHR (It is too big for the FR)
Have a great time
Regards,
TH