I don't really think you can do anything and once it starts you probably wont want it to stop anyway.

Lots of ladies do go early with their first. I was 38w 4d when I gave birth and I wasn't the first to go in my buddy group - I'd say about 1/2 of us went early & the other half went late so you do need to make sure you have a way of contacting him during that period that you normally can't. Surely there's a way around that. Once you get that sorted you will feel more at ease.

Just feel reassured that most 1st labours take a while so he probably will get there in time. Mine was 12 hours of pre labour then 15 hours 1st stage and almost 2 hours of 2nd stage so my DF could've got to me from just about anywhere in that time.