I Hope Your Family is Doing Ok. I wouldnt take a chance on driiving 350 miles with a P0740, its 50/50, it could just die 1mi down the road or it could take them all the home and then die.
its the clutch and solenoid paths between D3 and D2 that is the main issue, putting it in D3 will not help.
if they are still determined to try, and if they are in a safe location, i would at least have someone change the tranny fluid to a synthethic before they even try. that will at least give them a fighting chance. I would go as far as saying that use Racing ATF on half of it.
also depends on the model of the Ody, if its less than 2002, then no. dont even try. with a 2002 up, from my expereince, but still no guarantee, there is a good chance they will make it if they change the ATF to synthetic /racing synthetic mix.
if they know someone mechanically inclined thats willing to help, they can do the solenoid cleaning too. it wont take a whole day. that and the switching the ATF will give them a better chance of getting home. adding a cooler would also be advisable.
Keep Safe. Drive Safe.
CK