Curl bars can used for most lifts, just hold them more outside where the bar is straight. Gyms that offer aerobics classes usually have small bars that you can add weights to that only weigh 5-10 lbs, or they have bodybars (fixed bars covered with a pad that go up to 30 lbs).
Place a block of wood or some rubber mats or use a power rack to raise up the height of the deadlift if necessary and watch form, kids often have no idea how to control their lower back in a deadlift.
Goblet squats should be a good choice, and I would suggest that a good chunk of their training be focused on bodyweight exercises - safe, very effective, the load grows as they do, and it teaches them to control their body (functional if you prefer).