Warmth is vital. If your DH is cold he will hate it. Even in summer it can be very cold at night. Take full waterproofs, loads of layers, ideally including a thermal top and leggings, plenty of warm socks. A hat and gloves are a good idea although hopefully completely redundant. Of course you may have a stove in your tent and maybe a campfire in the evenings so you may be quite warm anyway.
For the children the same with the addition of a fleecy onesie for night time and sleeping, and wellies for walking in the early morning dew even if you don't get rain. Toddlers do well in all in one waterproof suits and can pretty much spend the day in them and crawl wherever.
Bring a few blankets for wrapping up round the fire. Bring marshmallows and skewers for toasting round the fire.
Earplugs are a great idea and maybe a n eye mask like you get on flights to avoid waking too early.
Equipment will depend on what they provide but folding chairs and a picnic rug are a good idea. Also torches for everyone, preferably head torches to leave your hands free.
Maybe a table if they don't provide one though I am sure they will.
If you like real.coffee bring a pot and some proper coffee so you get a nice brew in the morning.
Toys, books and colouring in for the children. Always a ball.
Hard to say more without knowing what is supplied.