Grand Canyon 2014- first looks

So, next year, Dean and I are going to the Grand Canyon.
I am still trying to decide whether we are going on our April vacation or in July.
April - my brother will be here. He can go with us. ... But I worry it might be too cold. Besides there is one part - the North Rim is closed.
July - Little Brother might be gone and ... it is the rainy season - which brings lightening storms.
I found this information here:
http://www.nps.gov/grca/planyourvisit/things2know.htm

Here is the link to the main site:
http://www.nps.gov/grca/index.htm
I have to go back and figure out how major is the Grand Canyon North Rim - and how great a loss it is not seeing it. I mean, if we are going to go all the way there, we don't want to miss something major - like me missing Paul in London... (idiot!!!)

and here is a link to some commercial sites - for train rides ... I have not spent time on them yet.
http://www.canyontours.net/?ctt_id=1735753&ctt_adnw=Google&ctt_ch=ps&ctt_entity=tc&ctt_cli=11x23045x69402x513836&ctt_kw=grand%20canyon%20attractions&ctt_adid={creative}&ctt_nwtype=search
http://www.canyontours.us/