The safe answer for me to give is 'I don't know' about the washing powder. I've looked at records for Unilver, Procter & Gamble and Reckit and Colman. They have all use Guinea Pigs for testing of washing powders. All have stated that the animals were examined after 21 days of breathing microparticles. The animals were bred to be susceptible to asthma. It had an effect on some but not others - none died, according to the sources I have found.
Washing up liquid - no harmful side effects reported.
I would apply washing up liquid and don't let the guinea pig on the grass until the following day, after I watered the lawn again with plain water. I wouldn't risk my pet.