How fast would you expect to be working on "current" in game content? By that I mean having characters who will be high enough level to access the current expansion and put it to use.
If you expect to spend your time relearning the game and not particularly rushing to be max level and all, I'd go with the House of Thule expansion, you can find it for $20 pretty easily (Amazon, likely Steam as well). That would give you access to all but the most recent expansion, level 90 cap, and all past expansions included. The one thing to note about this is that in March EQ will be going to its 'Free to Play' (F2P) options that will basically give you House of Thule as a default.
If you haven't seen the F2P news, the totally free option is rather limited on a lot of things and unappealing to most, though older accounts/characters will be getting grandfathered into slightly less restricted free version. F2P is set to go active March 16th.
Veil of Alaris (The current expansion) will probably cost you $40. A rough expectation is that you wouldn't really put this expansion to use until level 85+. It is a pretty difficult expansion overall, so you would also expect to need any character venturing out there to require lots of AA work. That being said, if the extra $20 is no big deal, VoA also has some added functionality to things like the UI mechanics that may be worth the purchase starting out.