It’s difficult. Poor wee mite.
I wouldn’t say anything along the lines of ‘work for’ or ‘shorter days’. He’s at an age where he thinks his nanny just looks after him because she loves him and that’s nice, don’t spoil it.
Hopefully she’ll still visit & maybe babysit? Come for the weekend (paid) if you & DH want a weekend away etc.
The friends Mums have become friends with your nanny, that doesn’t often happen, most parents only want to be friends with the parents, not the ‘hired help’. Sad but true. So hopefully they’ll be open to becoming friends with your new nanny, but no, you can’t expect them to click as friends even so. However, the kids are old enough for independent play dates. It’s not quite the same, but it’s something.
But yes, it’ll be difficult for you to have someone new looking after him & doing things differently.
Personally, I’d be tempted to get a temporary nanny because I think your nanny’s new arrangement will be far from fabulous and she’ll be kicking herself for leaving 😖