Maybe a bigger gear. I would get a different cog though, unless your surly is an 05 model (Surly cogs have a very narrow thread section and are known for stripping hubs). You can get a Dura Ace cog for about $15.
http://www.sheldonbrown.com/gears/ - this was helpful to figure out gearing.
Personally I like 46x17 in San Francisco. It is a very personal thing though. Your step son will probably be playing with the gearing no matter what is on the bike when he gets it.

About the freewheel. I had one on my bike on the flop side for months. Never used it. Took it off. I sure don't miss it.

Hope this helps!