First, what are the different ways characters react to Atticus taking the Tom Robinson case? Second, based on these reactions, do you think Atticus...

In Chapter 15, Heck Tate tells Atticus that he is uneasy about Tom being moved to the Maycomb jail. An entire group of men go to Atticus's home to express their uneasiness. There is no indication that they object to Atticus defending Tom. But they are worried about reactions from other people in town. 

Atticus meets with another group of men at church and they discuss the same concerns. These people that Atticus talks to are only worried about the backlash from the more racist elements in town. It's not that they disapprove of the principle. Jem and Scout are also concerned when they see how many other people are worried. When Atticus goes "out" (to watch over the jail that Tom is in), Jem is so worried that he follows him. Scout and Dill go with him and the children essentially break up a mob that had come to get Tom Robinson. Mr. Underwood is also concerned for Atticus and Tom, so he guards Atticus that same night. 

This all occurs in Chapter 15. Of course, there are some people who aren't worried about Tom, Atticus, or the children at all. This is the group/mob who come to the jail for Tom. They clearly disapprove of Atticus taking the case, but their main gripe is with Tom and his alleged crime. 

Of course, Bob Ewell takes offence to anything and anyone involved in the case. Atticus notes that there is nothing really significant to fear with Bob. But in the end, Bob does attack the children, so you could argue that Atticus did risk too much. However, if he had refused the case, he would have been setting the wrong example. Atticus could not have foreseen that Bob would stoop so low as to attack the children. And there is proof that he has given careful thought about how Bob might retaliate, long after the trial. In Chapter 23, Atticus explains why he did not retaliate to Bob spitting on him: 

Jem, see if you can stand in Bob Ewell’s shoes a minute. I destroyed his last shred of credibility at that trial, if he had any to begin with. The man had to have some kind of comeback, his kind always does. So if spitting in my face and threatening me saved Mayella Ewell one extra beating, that’s something I’ll gladly take. He had to take it out on somebody and I’d rather it be me than that houseful of children out there. You understand? 

Atticus thought that Bob might come to get him and that was worth the risk. There is no textual indication that Atticus felt his children were ever in any danger from Bob. (But the fact that Bob beat his own kids is significant. So, there is no clear answer here as to whether Atticus risks too much in regards to Bob's retaliation. One thing is clear. In the grand scheme of things, Atticus did the right thing by representing Tom. Doing the right thing, for Atticus, was worth the risk.)