Work /training affecting benefits ESA/DLA

My son is now on UC but was in the ESA support group, and is also on the lowest level of DLA. After years of social isolation (not engaging in activities or voluntary work etc) he has decided he wants to embark on some kind of training/work and on a whim went into the local job centre. I don't think he's filled in any forms yet, but I'm obviously concerned about the impact this could have on his benefits, whether the various authorities are alerted as a matter of course and if this triggers re-assessments. I don't want to be unduly negative to him and dissuade him from pursuing this as at the moment he leads a very solitary life, but I also don't want him to be coerced into anything that is unsuitable or that could affect his financial stability.

He'll need a lot of support and I hope the staff are trained and experienced in dealing with people who have mental health issues.

Has anyone any experience of a situation like this? I would welcome any comments.