If the passes are already expired (as in this year and not next year) then no you can not get a renewal price. The last I heard (but this changes all the time) was that to do a renewal you have to send in for the pass, and it expires 365 days after the date of your pass to be renewed. (so basically it's efective the day after your old pass expires). They have been doing this for the past few years where you can only continue the pass. I think you have 30 days to do this, but it still is only good from the end of your last pass.
They have never allowed the 10 renewal discount to go for more than 30 days. (At least not in the 13 years I've had a pass.
They have always allowed you to change pass options, so I don't think there's a problem with getting the two park annual pass at the discount rate if it's available.
There are no discounts on AP's. If the pass costs 103 and you buy a discounted ticked for dd for 23 instead of 33 and use the ticket on the same day to buy an annual, then you pay 80. Also I think the Alberstons coupons are only for adult tickets not child. (but seeing as I haven't seen one in person (even though my mom has a ton of them), I'm not sure on that one)
Have you been to DCA yet? There is not an awful lot of young ones to do. Most of the rides have a height limit of 40+ inches. (I actually think most are 42, but can't remember). My daughter who will turn 3 in dec is just barely 36" with tall shoes on, and can't ride most of the things at DCA.
That said, we are planning on getting a two park next year (might even do it in Dec for our birthdays (we all have december birthdays) instead of wait until March when ours expire, so we can see what they do there for christmas. And I'm not wishing we had done it in the first place since I would have like to have gone to see the electrical parade, WWTBAM, and some of the other shows and stuff.
Don't want to discourage you from geting two park passes, but if you've never been to DCA it's a shock to see who little there is for little ones (although since that's DCA's major complaint, they are trying to make it more kid friendly). I just thought you might want to check it out before commiting to the two parker.