What to tip a caterer for setup and delivery, but no service or cleanup

Our wedding is in less than 2 weeks and I have no idea what to tip the caterer. They are delivering our food and setting the food up, (we are setting all the tables and chairs up and provided our own plates and utensils, etc) but not serving it as we are having a buffet and they are not cleaning anything up. We have to return all the serving utensils and chaffing dishes to them the following day. Our total bill pre tax is $1077 and tax is $70.00 for a total of $1147. Invoice states gratuity is not included. If they were staying to serve everything I would tip 15-20%, but with no service and no cleanup, I have no idea what to do. Also, who do i give the tip to and is it okay to include it in the check when I pay the remaining balance?