When the kids are moving from one household to the other they will likely be stressed. Did I forget something? I meant to do this or that for mom/dad and I didn’t or wow it is great to be with mom/dad. Whatever the situation they will have a reaction.
Give your children ten or twenty minutes to just chill after a change in households. Let them put their things in their rooms, pat the cat/dog and just breath for a few minutes (hence the importance of the snack). Forget about homework or rushing to get dinner on the table
After a few minutes you can get going with the regular routine.
A pause is very beneficial. It really is a life skill that all of us should be doing. After something stressful has happened, good stress too, a time to reflect and just unwind will keep everyone calm and focused.