Not no ex-lax but maybe put some roses in the kitchen with a card saying , had a good time the other day, on the counter,that will keep him guessing.
You dont have to be rude to him but make sure he understands that life moved on without him and some changes happened and dinner time might be one of them.Try to do things different when he is there,so it doesnt seem as he never left.Maybe do a little changes around the house. Ask a friend to call you during the time he is there,and talk on the phone while your hubby there,just some suggestions its the smallest things that make them wonder.
Do hope you enjoy yourself though