I’ve known several [name_u]James[/name_u]’s who’ve just been [name_u]James[/name_u] so it’s not out of the question but the problem is, people will use a nickname if they want to and you can’t always control that. He might even decide he wants to be a [name_u]Jay[/name_u], a [name_u]Jamie[/name_u] or a [name_m]Jimmy[/name_m].
My name is one syllable too and my Mum liked [name_f]Grace[/name_f] but not [name_f]Gracie[/name_f]. Generally I go by [name_f]Grace[/name_f] but people do still call me [name_f]Gracie[/name_f] if it takes their fancy.
Should all that stop you using [name_u]James[/name_u] if you love it? I don’t think so. If you only call him [name_u]James[/name_u] at home, he may well grow up to correct people who try to nickname him 
I personally think the available nicknames for [name_u]James[/name_u] are cute, but they’re also very avoidable if you don’t want to use them. I know a lot of guys named [name_u]James[/name_u], and not a single one under age 50 goes by anything other than [name_u]James[/name_u]. (Some older Jims/Jimmys, but more recently it seems like no one nicknames them by default).
I love [name_u]James[/name_u] and it’s much better than [name_m]William[/name_m] imo though both are great. I don’t think you would have to worry about nn too much since the nicknames are longer than the name itself.
I love [name_u]James[/name_u]! But I’m sure he will get nicknames during his life you can’t really control that… Sure as a baby or young child you can insist on it but after that its up to him and others. Maybe [name_m]William[/name_m] [name_u]James[/name_u]? A middle name is not going to get messed with.
I can’t believe I forgot to say this earlier! [name_f]My[/name_f] cousin is named J@mes, his mom HATES the nickname [name_m]Jimmy[/name_m] & they can’t call him [name_m]Jam[/name_m]!e due to an ex. He’s three & hasn’t had anyone insist on them, but he still has nicknames — [name_u]Jae[/name_u] & [name_m]Jamesy[/name_m]. I honestly don’t think nickname-proof names exist.
James can be just [name_u]James[/name_u]. Most of the Jameses I know under 25 don’t have a nickname. I prefer [name_m]William[/name_m] with your daughters’ names though. They’re all the same style but the syllables in [name_m]William[/name_m] make it fit better.