On the Sunday morning, we opened the hall door so they could have the run of downstairs. Once the dor was open, it will stayed open. Izzy, our older cat, kept trying to get away, so we took her upstairs and she stayed on the bed. Shelby tried the cat flap, but its microchip operated and she isn't programmed in to it yet so she couldn't get it to work.
They've went everywhere, in everything, under everything, and they are fascinated by the christmas tree (I didn't put any baubles of decorations on the bottom half, so they are just biffing the branches).
Shelby followed me upstairs into the bedroom, and Izzy just glared at her. A bit later, Shelby jumped on the bed, and edged closer and closer. Eventually she tried to sniff Izzy's face, and Izzy growled a bit and then just got off the bed. We think that went really well! Not ready for unsupervised mixing, of course. Geoff took Izzy into his study, which is one of the few remaining kitten-free zones (and it will remain an Izzy only space for the forseeable future), so she didn't get overwhelmed.
Downstairs, Izzy would sleep on the cat tree, and Shelby slept on the sofa opposite. Mostly, Izzy ignored the kittens. The kittens were fascinated by Izzy. They kept wanting to get close to her, climbing on the back of the sofa or up th cat tree to reach her. She would growl at them, and then hiss or biff if they got too close.
If they persisted, we removed them. We didn't want Izzy to get stressed out. 
Downstairs again, Shelby had been watching the
chickens in the garden
and could hardly contain her excitement. We're
currently slowly merging a flock of 5 pullets from this years
hatch in with our existing old ladies, and none of the garden is
fenced off so there is plenty of room. This means that, from
time to time,one or other of the two flocks congregates around
the back door (anfd, if its the youngsters, they peck on the
cat flap). Shelby came round the corner to see a few hens
stadiing just the other side of the glass door, and she charged
at them, ending up standing on her back legs with her body
against the glass. The pullets are used to being ignored by my
other cats, so being charged at by something was a bit of a
shock. And of course once the alarm went up, they all started!Shelby is definitely the bolder of the two. She's fearless in her investigations; she's happy to be stroked, but has no hesitation in mobving off when something more interesting comes along, or she's had enough. Lewis is a purr monster, and loves having his tummy tickled. He likes to look out of the window, but isn't fascinated by the outside
More visitors arrived on Christmas Eve, and the kittens didn't bat their eyelids. They continued to be happy, payful, well adjusted kittens.
Izzy was brilliant with them. As the days progressed, we saw that she would sometimes let them pass without growling. Yesterday (New Years Eve), Izzy and Shelby nosed each other. Shelby was so excited she came back a second time. On the 3rd time, Izzy had had enough and growled at her, and she backed off.
We also noticed that Izzy started to watch with interest from the safety of the cat tree, rather than watching without being seen to watch.
We aren't home and dry yet, but we are really happy with the way it has gone so far .
.
