Went with the slightly newer account and it looks like I picked the wrong account sadly! Don't really feel like dropping the extra money on another monthly fee though, so I will just stick it out with this account and put SA on it.
Not sure about shards.. Atlantic seems to have the best population, but I am West Coast so that's a 120ms ping. I seem to recall the game being a bit picky about latency at times.
Any shards that are particularly old-newbie-friendly?
Well crud - sounds like we share the same kind of luck. I would have ended up with the wrong account as well. Perhaps you could spend the next few weeks relearning the game and then see about switching accounts and then upgrading? SA is well worth the cost if you ask me, but you will most likely not need it nor be ready for most of it in the next 30 days. Save for the new Gargoyle race and some of the new skills. Alternately at some point in the future you could re-sub the older account and "loot" the goodies. Honestly though skill gain is not too bad these days and New Haven can get you into the 50's within a few days of casual play.
As to shards... at this point you have East coast and West coast for North America, but you are free to choose any shard. The new Enhanced Client will help you pick a shard based on current online population. Unless you plan to focus on PvP the ping times seem to be pretty fair across the board so really it is about you typical play time and which shard would fit that best. If PvP is of interest then pick a shard with a better ping.
I am also a fan of reading some of the shard specific forums to get a flavor and feel for their community. Not all players use these forums, but it may be better than a roll of the die.
I have played on Lake Superior, Grate Lakes, Sonoma and currently spend my time on Catskills. All have great communities and seem populated enough, but Atlantic is by most counts the most populated. At the end of the day you should be able to find a group of friendly people to play with no matter which shard you choose. New Haven is a great place to look for help.
Best of luck and if you end up on Catskills or Lake Superior give me a shout!