I guess everyone's work flow is what suites them. Me personally would never go from source video footage (whatever that is for you besides your pics) to 1280x720\30p as a intermediate "Produce" to a forced 720x480/60i when you create a Menu based DVD if you use your "Produced" files as source for your DVD. Too much format jockeying to maintain good quality for me.
Basically you're going from source (probably interlaced) to progressive to interlaced
as well as 1920x1080 video source (most likely) to 1280x720 to 720x480
I follow these basic steps:
1) Always produce to your source video footage format
2) If (1) is not possible, then produce to highest end product target you envision. So if one thinks you might make a couple of BD's as well as DVD's, then always produce to the BD spec of your desire (H.264 1920x1080/60i 24Mbps) works great for me as that's most of my source footage is as well.
If all you have is slideshows from pics and no source video footage and your final target is a menu DVD at 720x480 DVD-HQ quality then I'd produce all your 11 slide shows to MPEG-2 DVD-HQ 720x480/60i (8Mbps) as you are going to end up there anyhow. Yes, quality will suffer.
Jeff