When TJ got hurt, (I meant beaten up) why did they Logan children help him? Why couldn't he just do it himself? Why did he arrive at the Logan's place?

Because they're nice to help him get through it all. Though TJ annoys them with his mischievous ideas, they're nice to help him.

Well, he was hurt. Imagine YOU being hurt just the same way...what would YOU do? At least the children were nice enough to help him.