My eldest (9) wants to bivvy out (yay!), would people just recommend an adult bivvy bag? Do they even make kids ones??

Also, is it worth buying decent kids sleeping bags or just cinching in an adult bag?

Mostly this would be car/beach camping, but some bikepacking may occur in the future.

Ta!

I was out with a fella and his 12 year old (he wasn't a big lad) last week and he seemed to cope fine with adult sleeping / bivvy bag. As you say, it might be worth folding the bottom of the sleeping bag underneath to remove any 'dead' space.

AlpKit used to produce quality kids sleeping bags but I don't think there were any plans for more.

My 10-year-old uses a regular adult sized bivvi bag and sleeping bag (and mat for the matter) and he likes the room in there as he's the most restless sleeper on the face of the planet so thrashes around quite a lot.