I know the NEC like the back of my hand having been every year for Crufts on my own (and as a wheelchair user, you do a LOT of laps as the ramps are not suitable to get up alone in a manual chair).
This is way smaller than Crufts which is 5 halls, so you should be ok letting them go off in pairs or by themselves and actually they are likely to be less stressed and see more that way, trying to stick together in a group in a crowd is REALLY hard and stressful.
Identify a meeting point by GOING there AND noting it on maps, the place is big even if its only a couple of halls and can be quite confusing when busy and full of stands. There are also several identical locations (two Subways, multiple sets of toilets in halls that look identical), so pick something near a big external door, they all have HUGE numbers painted over them. Arranging to meet to the left of A5 for example is far clearer than 'meet next to Subway'.
Ensure meeting times are set, don't rely on being able to call/message each other, wifi can be really patchy and its usually too loud to hear ringtones.
Take easy to carry bags, take your own water and snacks, food is exorbitant and don't think you can nip out into the central area upstairs and go in McColls for cheaper food... they don't sell anything that directly competes with the stalls/stores inside the halls, particularly water.
If you want a meal at the NEC without huge crowds, its well worth walking over to the monorail and popping over to the airport for food, it won't be much cheaper... but there's lots of choice and less crowding.
Wear lightweight layers, it can get REALLY hot in there when it's full of people and trying to battle crowds, bags and extra coats is a pain in the backside.
Have fun!