If the sleeping areas are in separate pods, I would be inclined to have two double airbeds, and 1 adult 1 child in each pod. I think your little uns are rather young to be in a pod on their own.
I think ours were four and eight before we let them share a pod without us.
We started off having one double airbed for us and one for our 3 year old, but she woke up a few times in the night, so then we swapped. Myself and our daughter sleep on one and OH sleeps on the other. It also means that if we are camping with friends, he can stay up a while longer and jump into bed without catapaulting me off the airbed!
When we started I had the two children who were four and two in with me on a double airbed, - at one point I even had three sleeping bags zipped together when the double because slightly too small. Looked odd, but worked. I would definately go for one child with each of you on double airbeds. For me this was not an option,
Argos sell narrower size single airbeds 2 of which fit in the smaller 2 person bedroom of our Outwell Nevada M which should be the same size as your Montana. Our 2 kids dont like sleeping on a double airbed which is why we bought these singles
Myself, husband and 2 year old all have self inflating mats, that way we're all on one level, daughter can then sleep anywhere and fidget around and not have anywhere to fall either!
My two are 5 and 6 and I fear if we put them in a separate bedroom we'd be up and down like a bride's nightie in the evening and at dawn telling them to quieten down and go back to sleep. So much easier if you are all in together (or one adult one child) to just roll over and give them the Eye of Sauron if they are messing about.
We all sleep on sims. Much warmer and you can't fall off them (although my children seem unable to lie on them straight and there is always a bit of body or head draped on the floor which needs rearranging in the dead of night...again much easier to do if you are lying right next to them).
We also have smaller single airbeds for the kids in the weekend tent (the blue and red rubbery ones from Argos work well for us).
Our tent has one big sleeping area with a divider which we have never used. Our kids are 10 and 12 but still like to be able to see us during the night.
We have suggested they could have a pup tent this year but I have a feeling they will end up back in with us.
We have a Nevada M and choose to remove the divider between the 2 sleeping pods aswell. We just find it easier to be all in together - the children love the giant bed created by 5 airbeds squashed together, and we can keep them quiet if they wake too early in the morning x