Oh yes, boy have I been camping.
I would suggest that you look for campsites with either a common room/games room for in the evening - somewhere to go so you are not stuck in the tent. If it is raining it will get damp and cold quite quickly and then it is almost impossible to get warm unless you invest in a little Camping Gaz heater. If they are going to sleep on those rubber airbeds, take a couple of sheets to put on top (body heat will cause condensation and make the air beds wet and consequently you wake up at 4am absolutely frozen).
If you do have a heater, board games and card games are quite entertaining, even for little ones. You also need to consider how you will feed them. Will you eat out? If not, make sure you take plates, cups, cutlery, cooking equipment, a small stove, a washing up bowl. A cool bag is handy to store milk in and other perishables in (many campsites will let you put cool blocks in their freezers), but it never keeps quite so long. Given it is Scotland, you absolutely MUSt take waterproofs and wellies lol