I'm with Ed here. The fact that you're making multiple
casseroles deep dish pizzas at the same time will work if you are able to tend to them a bit more actively (i.e., trying to do thin crust might not be as easy). Depending on your oven, you might want to drop the temp down some (425 instead of 450), since the oven will be cycling on a lot to blast up that high. DD can go longer as needed, and you don't want to burn anything. If I were you, I'd splurge and spend the $16 to get two cheap stones to add some thermal mass to the oven.
I'd like to hear more about this event you're making these for. Are you having a big group over to your house? TBH, when I've done this, I'll make one that comes out of the oven just before people arrive, which means the second one is already in. Left in the pan, on top of the stove and uncut, it'll stay hot for a while. Or I'll make two beforehand--first comes out 30 minutes before arrival, second right around arrival, and third 30 mins after arrival. Seems reasonable.
An uncut DD is easy to reanimate in a hot oven for 5-7 minutes, if needed, especially if it was baked within the last 30-60 mins (i.e., not the day ahead or anything crazy).