In my household, I like my steak medium rare but the kids and wife like medium, is it possible to somehow cook the steaks with different doness in the same batch (2 different sealed bag of course)? My concern is that If I do them in 2 batches, then by the time the second steak is done, the first one would be cold already.
Your idea is almost exactly what you do.
There is no need to take the first ones out as you are lowering the temperature as they will not overcook.
Yes, this is a problem, especially when entertaining and steak preferences run the gamut of medium-rare to medium well (the horrors, I know!). I found manipulating various temperatures on the steaks in the sous vide bath is just too much trouble and time. Instead, I sous vide ALL the individually-sealed steaks to medium-rare only. Rather than using the APC to vary the degree of doneness, I do that separately as the finishing step.
My range has a grill unit in it but cast iron skillets work quite well too. I remove the steaks from the sous vide bath and put the to-be-medium-well steaks on the grill first, leaving the others in the bath. After 1-2 minutes then put the medium steaks on the grill, and lastly put the medium-rare steaks on the grill. Using a well-calibrated feel or a Thermapen, remove the well and medium steaks when desired, and they’ll have amazing grill marks. I give the medium-rare steaks one minute per side, rotating 90º at 30 seconds for crossing marks. For me, this results in perfect steaks, all ready to be served at the same time, and more quickly than trying to do the adjustments in the sous vide bath. This probably sounds cumbersome, but is very easy and quick to do. One concern is that there is some carry-over cooking effect for the more-done steaks so you’ll want to remove them from the grill about 5º or so before the desired temp.
That is a great idea. I am lucky all in my family like them medium rare.