If your goal is to maintain some mystery and imagination not to be stifled by the mechanics, I would say ..
ask them to come up with an initial concept using the info you mention sharing - tell them you just want to hear their initial concept first but then they can see the phb and come up with their character. then let them go at the phb at which point they can alter their concept if they want... or go with their concept,e tc.
sure, everyone may very well change, but some may keep some kernel of their initial concept in there.
that's just my mental thought process on the topic anyway. it offers some creativity and mystery up front, but won't result in people feeling bothered by not knowing the details when they create the thing.
another option - ask them for their concept, then you make them their 1st level characters as pregens. use these characters for one or two adventures. (tell them that it is so they can get used to the rules) and then after the predetermined amount of adventures, they can switch to their own-made characters (which they could have been making between sessions). they key to pulling this off, however, if making it clear that these are just temp pregen characters 'for them to get used to it so taht they don't waste bad choices on their own characters' - of course, it would be doing exactly waht you wanted though, letting them have a character based on concept and will maintain all the mystery and surprise and wonder, etc etc.
But hiding the phb from them the entire time is just pushing it. though i can see for a couple adventures to get their feet wet...