I’d only choose the longer form if you love it just as much as the short form – or if you’re getting something very valuable out of it like a family name. For me, potentially having options isn’t a big draw especially if I’m not keen on some of those alternatives e.g. he may choose to drop [name_m]Max[/name_m] and only go by [name_m]Maxwell[/name_m] or [name_m]Wells[/name_m] when he’s older.
[name_f][/name_f]I don’t think you’re tied to short names if you expand your family further. What makes [name_m]Leo[/name_m] and [name_m]Max[/name_m] such good brother names is their style and zippy sound, not so much the length. So you could totally have [name_m]Leo[/name_m], [name_m]Max[/name_m] and [name_m]Benjamin[/name_m] or [name_m]Leo[/name_m], [name_m]Max[/name_m] and [name_f]Charlotte[/name_f] no problem.