I like [name_m]Aidan[/name_m]. It’s charming, relaxed but grown-up enough and appealingly simple. Great meaning as well.
[name_f][/name_f]For me the natural spelling is [name_m]Aidan[/name_m]. I do see [name_m]Aiden[/name_m] a lot so you probably will have to clarify the spelling, but since [name_m]Aidan[/name_m] is a commonly accepted variant it shouldn’t be too much hassle?