Are funerals supposed to be kept on the sabbath?

It is more a matter of traffic control than anything else. Regular canonical ( within the Church norms of the Canon Law) Masses are on a regular schedule on Sundays- in the Roman church. Therefore it is extremely unlikely to hold a requiem or funeral mass on Sundays. This is more a matter of traffic control than anything else- the same, for different reasons, applies to Weddings. Weddings are usually held on Saturday afternoons ( to avoid tie-ups with the regular schedule of Masses) The Mass is ended, Go in Peace- Deo Gratis! (Thanks be to God!)