Shouldnt be too much of a prob as your moving in the summertime and the ambient temp is up so it will help maintain the temp of the water you will be transporting the fish in
Firstly you will need an insulated polystyrene box with lid (obtainable from your lfs usually at no charge)' several large fish bags (again lfs should let you have some), 2x battery operated airpumps and spare batteries newspaper towels etc to insulate the box further, and some large water containers.
Firstly catch all of your fish and distribute between the bags only fill the bags 1/3 with water so as to leave plenty of room for air add small airstones to the bags and rubber band the bags leaving the airlines sticking out of the tops.
Connect up your battery airpumps with adapters to share the air between the bags and put bags in poly box wedging them upright with newspaper towels etc put lid on box and forget about htem only checking every 2 hours or so, so as not to overly stress the fish.
Transfer the remaining tank water into your containers and put the now unplugged filters in a bucket with a tight sealing lid with some tank water.
If you so wish you can keep the bacteria contained in the filters alive by sloshing them around in the water every 5 mins or so but on a 12 hr journey this would soon get annoying lmao
, so my advice is to get a bottle of "cycle" treatment which contains millions of bacteria and is added to new setups to quickly establish them and add this when you arrive at your destination and set up your tanks again.
Do not feed your fish for 3 days prior to the move so as to keep waste down whilst they are being transported.
It is also a good idea to take 2 or 3 flasks of hot dechlorinated water to top up the bags with should the temp drop in them enroute, but only do this if you really need to as it can also stress the fish which are already stressed.
When you to the final destination first thing to do before anything else is to set up your tanks again (leave the unpacking to the missus lol) add the water from your containers heaters etc
Get the water up to temp asap and float your bags of fish as you would when adding new stock from the lfs, by now you will have added the "cycle" and filters etc release the fish after approx 15 mins and leave the lights off for a day to let them settle down.......with luck by the 2nd day they will be queing at the top of the tank for a feed lol
Expect to loss a few fish but that doesnt mean to say that you will.......just be prepared in case it does happen
Hopefully this helps as i have had to move fish over long distances before and know only too well the pit falls that come with such a task but at the same time i have rarely lost any fish by doing it this way