merging flocks

Sadly, since my last post we no longer have our two hens Sam and Ella, Sam died and Ella went AWOL the next day(We assume looking for her coop mate ?).
Unfortunately they left behind 3 ten week old chicks that they had been bringing up between them, so, deciding that they needed a bit more instruction in "The Way of the Chicken " we brought 2 mature ladies to bring them up.
The chicks have been kept in the ark that they were hatched in (they are now 16 weeks and one's a faverolle, so space is getting tight !), and the ladies in a separate coop.
 My problem is this,
To save us having to get up in the dark/wet/cold to let them out over the winter, We would like to move them all to one (warmer) converted dog kennel/ brick shed(aprox 6' X5') that has an attached, roofed, dry run area with a secure lockable door that We could open at our leisure.
We have started keeping their food in the run, and the ladies are laying in the shed, so they are quite used to it
so,
Could anyone advise me of the best way to do this, ie, do I just put them all in one night and let them get on with it(they are all out together during the day, but keep to two groups, but the ladies are at the top of the pecking order and are quite brutal with the chicks) or do I try locking them in the run during the day and see how they get on ?
Help!
Glyn

Thanks orchardlady,
I sort of figured that's what I'd have to do, but it's always better to hear it from someone else who knows what they're doing !- good tip about the torch - I'd better do this sooner than later, I've just watched Big Dopey (the faverolle) bang their head trying to get into the ark !

I have a large 8ft by 4ft bit of 'fence' covered in heavy wire that I put in a corner of my chicken house for a day or two so the birds can see each other but not fight, and I ALWAYS introduce new birds in dead of night when everyone is stupid with sleep. My 2 ex-broiler hens chase my young pullets outside in the morning as soon as the doors open. I think they want peace to lay! A fight can be scary, the biggest broiler Audrey dragged my young Cream Legbar rooster around by the scruff one morning and the noise was incredible, but they were fine. I have the luxury of a 30ft by 10ft loft for my 13 hens so you need to be extra vigilant in smaller areas.

Well, We finally got round to putting the hens in together last night and I don't know who was more traumatised me or the chickens !
We lured them into the run with lots of corn about 20 minutes before they usually retire for the evening and then locked the gate - chaos ensued - with the chicks frantically trying to find a way out and the ladies making bellowing noises that I didn't think a chicken could make As it got darker and darker eventually they calmed down a bit, and the ladies went into the shed, hopped up onto the perches and settled down. The chicks reluctantly followed, except Big Dopey who decided she was going to sleep in an oil drum that's laid on it's side in the run. We waited until it was fully dark and went in picked her up and put her in with the rest of the hens.
One thing I didn't count on is that as the chicks have been brought up in an Ark,  they are not used to perching when they roost, so I've had to do a bit of rearranging of the shed to give them more room, so they're not sleeping below the ladies
So at the end of the day I think we can chalk that one up as a success - let's see what happens tonight !