They're an asset to him as family and as supporters, but they are not an asset to him in policymaking and decision making. They have no experience or background in major policy matters a president must deal with, and they will end up harming him and his presidency because they are leftists, and Trump did not campaign as a leftist.
People like you whined when Ivanka met with Al Gore. But, that had zero impact on Trump's position on environmental policy or climate change.