Would you do it?
I would leave him with DP and DM. DM would do the nursery runs and look after until DP is home from work.
It's that, or cart him off with me to the other side of the country and back for those days, and stick him in nursery whilst I'm there.
It's also only temporary / 6 months max.
I won't explain the situation as it's quite unique so if someone reads that knows me, they'll know it's me and I'd rather have my thoughts 'private'.