Reg should open in June or July like last year. You mentioned that you signed up for the email alerts, but make sure to reg as soon as possible. Last year it sold out in a month, the DL 1/2 sold out a few weeks ago in 1 day!
You
can do both the 5k and the 1/2!! I do and it's so much fun. The 5k is Sat at 5:45 am and the 1/2 is Sun at 5am, if they keep the times like last year. The 5k is entirely in both parks and back stage, the 1/2 is around the parks, in the parks and then around Anaheim. The 5k is a fun run where there is no time chip, but they have times at the mile markers and the finish. As long as you're moving forward and not dawdling, you won't get swept. If you are going to do both, go easy on the 5k that way you're not too tired for the 1/2.

It's also a good way to take pics in the park w/ the characters and that way you don't have to carry a camera during the 1/2. They have mostly bands and cheerleaders outside of the parks, but no characters.
The 1/2 has a 16min time limit/3:30 overall, and the time starts when the last person crosses the start line. They have different points along the course where they have sweepers. You're corral is based on the time you think it'll take you to finish. You can submit any time you'd like, but if it's under 2:45, you need proof from a previous race over 6 miles. You submit a time when you reg, and if you run a faster time before the race there's a time period when you can submit it to move up. You can also do this at the expo.
As for your husband, he can actually do both! W/ the 1/2, the closest corral he could be placed in, regardless of time, is in C (he submits time just like everyone else). That's mostly b/c the race is geared towards women. I think there were 1,300 men that ran this year. But if he does do the 1/2, make sure he checks the t-shirt w/ the unisex/men's sizes, they have both.
Hope that helps a bit!