GP 14, Mirror, Wanderer (Smaller lighter wayfarer), Wayfarer, or Drascombe for any serious cruising. Gull is quite tiny but mighty. GRP or Ply so you can fix it. Plastic stuff is less likely to break but harder to fix. You’ll not get anything that can take a load and kids on a vehicle roof.
Wanderer and Wayfarer groups are very active and have trial days. pending covid!
You sound like a beginner so join a club, try their boats, maybe start with a topper to see how keen the kids are then cruise when you have experience.
I’ve sailed lots,(I sail a wanderer) but first months of this year will be day sails and capsize training for crew and me before we even load a tent. If we are ever allowed!
If your boat is cheap, budget another £400plus for sails as it will be frustrating otherwise!