I think I'm going to have the best of both worlds. Am lucky enough to be working in own firm - can therefore take a day off in week if want to. DOH does not work on Fridays. DDIL will be going back to work very shortly three days a week. Her parents will be having DGS1 two days and we will be having him on Fridays. We will be alternating Thursday nights. DS is a teacher so will not be having DGS1 during school holidays.
Arrangement means DGS1 gets to spend quality time with both sets of GPs and more importantly, with DS on a one to one basis. Also, this way, there is no large financial burden on either set of GPs - they will collect and we will collect from them and drop him off at home/meet up with DS or DDIL to drop off.
Of course we will still see them all at weekends and during holidays in same way as do now.
DOH and I are younger and more active than DDIL's parents and will be doing different things - we'll do the walking, running, surfing, beachy, muddy things while DDIL's parents will do the quieter shoppy, crafty, visity things. Hopefully DGS1 will find that he has the best of both worlds and can have different relationships with us all.
Nobody feels left out and nobody feels put-upon. We do seem to be incredibly lucky that we have been able to work it out this way.