How have you brought so much stuff that you couldn’t take it on the plane with 2 adults and a baby allowance in the hold? I travelled to Spain alone just me and baby, Dh at home. And just packed our two carry ons, plus pushchair in hold with assorted things in pushchair bag. Anyway, mistake 1 for way over complicating things.
Anyway, we’ve done many a 9 hour drive since having children and dh didn’t take to bed the whole day. You have to just keep parenting because that is life.
A beach/pool holiday is a bit boring with a baby, but if that’s what you want to do, you break the day in two. You each take a time slot where you get out with baby (I mean literally go out somewhere and do something stimulating and interesting, I did lots of museums and botanical gardens, go sit at a street side cafe, go for a walk). And then the other gets to rest by the pool/beach for several hours. Come back for some or most meals together. Swap over.
If you are in a hot country, afternoon nap quiet time indoors. I just curled up in bed and slept for a couple hours with mine.
If you are self-catering, you can put baby to bed at normal time and then you get your evenings with the adults. But generally, I adjust mine to late nights, so we go out for dinner and they are either up or sleep in pushchair until we go to bed at 10pm ish.
My rule is that if we are with dh’s family, it’s his job to get up in the mornings with the dc and facilitate them spending time with his family. I don’t get up at 6am and do all the wrangling and the coffee and breakfast and early morning entertaining. He wants to spend a week with his family, he spends time doing that stuff with them, not me.