Find out what they actually do value and why. Usually, if they are both working they are starved for time for themselves and a good rest. If you plan something and do most of the work and make it a fun event instead of another task, there is a good chance they will want to come. Also, do they understand that it is important for the kids to always be connected to their family and then do not criticize them or the kids when they are at your house. Some day they will realize that their family cares about them more than anyone else and finally "get it." Until then, keep trying.