You’re pet is part of the family shouldn’t they be part of the festival? It all depends to what length one goes with their 4 legged/ tail wagging friends. For just like humans the need of life supersedes that of observance and if you’re pet will truly get sick on the Passover dish’s I’m sure G-D will give them a pass. We also don’t have any paw prints that they were free of slavery and they still have a leach to prove it so maybe it’s best not to overdue their observance. Therefore a little Matzoh might be in order but remember their health is 1st and ask G-D to let them have a pass over if the Gefilite fish doesn’t swim.