Tiffini,
I don't have much experience with DITHOR yet...but here's what I do know and what I remember reading. I'm pretty sure that when you get to Preparing, DITHOR is scheduled every other day, and if your child is ready for DITHOR before then you can decide how often you want to do it. I think there are a lot of moms that use it every other day...which covers the 9 genres over 2 years.
I just started DITHOR with my 8 yo and so far it has been very quick and fun for us!

(Not that we were expecting anything else...he's been begging for the books for the last 8 weeks.

) You get to set the pace for your reading, so you kind of decide how long a day takes. It's been right at 20 min so far for us. I'm planning to do it every day this year while we do Bigger and then next year it'll be every other. (You're doing Bigger, too, right?)
You mentioned alternating days for your 8 yo's. I think that would probably work really well for you. Here's another idea...you could alternate the days they read aloud to you and read silently. I don't get the impression that 8 yo's
have to read out loud all the time with DITHOR. I think that's your call on what they're ready for. It also mentions in the guide that you can get them started by listening and then "turn them loose", so that's an option, too.
I'm sure some more experinced moms will be along to give us ideas.

I'm going to get this submitted before I loose it
again! (I have no idea if I said the same thing this time...

Oh, Kelly... You have those cute little jumping icons, surely you know where the "lost and found" is on a message board. Unfortunately, I think I have several posts there.

)
Looking forward to going through DITHOR and Bigger with you!

Kathleen