Well personally I really like Alex and I hope he does well in this venture and that it will lead on to other presenting roles.
My first thought was that, even though I was pleased he had got the role, I wouldn't have thought childrens presenting was ideal for him, but then I remembered how well he did on the Disney awards. He seemed to get on really well with the kids then, so maybe it will work.
Nickelodeon is a very well respected children's channel, in fact it is number one in the ratings for kids TV and has been since 1997 apparently, and several mainstream presenters have started their careers there.
Good Luck Alex.