If they are fighting a lot they have a lot of adrenalin rushing around and negative feelings, so long walks are good, like jellyfish has said, this is calming for many kids, helps level out emotions and helps them connect with different parts of their brain - apparently when in fight or flight mode they are in brain stem and walking and trampolining helps things reconnect. Good for you too! I think your two are too young for trampolining, in that doctors don't recommend it, but definitely when they are old enough, I found trampolining to be amazing therapy!
I would really recommend teaching them about behaviour and being kind - a lot - you probably already do this. I don't personally think telly is very good for traumatised brains, but having said that there are lots of really good youtube videos aimed at around 3 or 4 year olds I think, ie young children find them engaging, about things like "helping hands" "kind hands" letting out "mads" (lots are made by the US). I think videos of children getting on and being happy and warm and fuzzy helps children start to remember about different ways of behaving.
I used to find some cartoons are better than others in terms of affect on behaviour. I found Ben and Holly and Postman Pat and Little Red Tractor were great as there is lots of calm and kindness and happiness modelled. Lots of the other cartoons are super in terms of content, such as Octonauts, but just too frenetic for traumatised brains, or at least, were too frenetic for my dc at that age. It probably very much depends on the child.
Lots of reading, and lots of books about kind hands, being friends, being kind.
Joking with them about the fighting, asking who is going to lose a limb today.
Being a dinosaur or monster, running around chasing them to get them out of fighting mode - apparently 10 mins of this a day works wonders (if they enjoy it).
All kids are different though, with one of my dc literally the only thing which could break them out of fighting mode would be to get them to sit down and do drawing - instant calm and focus!
In terms of keeping yourself calm, I found that if I woke up expecting the worst for the day I coped better. Your mind seems to subconsciously prepare itself.
When you are calm maybe sit down and divide a page into 2 columns one for each child and think about each separately in terms of their triggers, their needs, how to meet their needs, strategies.