A long weekend in this country, where you could get back in case of emergency- yep, ok, lovely thought. But even that would need to be accompanied with a plan on easing child into being looked after by grandparents regularly during day, then at least a couple of overnighters. Slow and steady. It’s not just the child who needs to get used to be left, but checking gp can cope, follow “your” reasonable rules so it won’t cause chaos when you get them home (like sleep times) .
a whole week, abroad, nope. I’d certainly not go abroad at all with both parents, without children, even at any age, too far to get back if something happened. They’re not random relatives even if they’re teenagers- they are your dependants and legally your their guardians. No one can make decisions without you.
I think it says something about his stage of bonding with baby. He can still separate the two of you from baby, and think that’s more stress free. To you being separated is more stressful. Like a lot of dads thatll start to change as baby becomes a toddler and more independent from you . It may say something that dad now needs to start to have more time to bond with baby on his own, and find stuff that are just the two of them to do - do you really encourage that ? If not, don’t make the link to him, but start to do that now. Weaning is coming up soon so get him really involved with that and taking a bit of a lead role etc
if DH doesn’t want to spend that time, or step up into more proactive parenting role now baby is getting older, then you have a bigger issue really, that the surprise holiday is a small part of.