"You can travel to outdoor open space irrespective of distance, as long as you can return the same night and do not put others at risk because of services you may need in the time you are away."
Otherwise, it seems your plan would be following the guidance (as long as you stayed 2m apart, and follow the advice in point 1.9).
Edit: Actually, reading that again, it says "as long as you can". It doesn't say you should return the same night.
The guidance (point 1.12) says:
"You can travel to outdoor open space irrespective of distance, as long as you can return the same night and do not put others at risk because of services you may need in the time you are away."
Otherwise, it seems your plan would be following the guidance (as long as you stayed 2m apart, and follow the advice in point 1.9).
Edit: Actually, reading that again, it says "as long as you can". It doesn't say you should return the same night.