hmm... I've met a variety of Alans - varying from the rather sweet mild-mannered clever fellow with floppy hair, to the shaven-headed thick-as-mince gobshite - so it depends on which of them occurs to me first.
All the Alans I know are over 40 - so the name will be underused for babies - lots of people will know a few Alans with good and bad associations - these Alans will be dad and granddad ages.
It's not a retro name that's back in fashion like Alfie, Archie, etc., and because it's not in fashion people are going to assume little Alan is 40 years older than he is.
There are a few spellings: Alan, Allan, Allen (I think the double 'l' versions are surnames used as firstnames), Alun and possibly others but I can't bring any to mind just now.
As with all baby names, if you really like it, and you think it will be okay in the playground, and if the initials won't spell anything undesirable, then go for it, and don't worry too much.