You want a lightweight, easy pitching tent, like the Woodville 3 or 4. These also have a porch area, which is great for muddy wellies. Air tents are the fastest and easiest to pitch, but weigh more.
For maximum warmth and comfort, sleeping bags need to be a close fit so it’s important to invest in junior sized sleeping bags for the kids. Self-inflating mats are easy to carry and set up.
Blankets are great for picnic-style meals, or try the Dawson Picnic table set, which comes with a table and four chairs that fold down into an easy-to-carry suitcase.
Eating outside is all part of the camping experience and it’s likely you’ll be cooking at the campsite fairly often. The Jimbu stove is a portable, lightweight stove and grill in one, so you can toast and boil whatever you fancy.