Medical is valid ..
Medical documents once submitted to INS are valid for ever. They do not question that . Only if some column is not checked or filled up properly by the doctor, will they come back to you.
But since you are going to the local office, better play a safe game.Get your medicals done again.
Get the affidavit of support for your wife and kids(I-864 notarised), even though they have not asked for it .
Make copies of all documents that you have(passport, W-2's, pay stubs, and what not...). They might ask anything(After all you have to understand that they are dumb people).
Good luck..