The connection Miranda - Bonito is made by the company Cruzeiro do Sul (coming from Corumba) each day except on Sunday. Bonito is good (Rio Sucuri is the best) but a little expensive. From Bonito to Foz do Iguaçu, you don't have to return to Campo Grande. There is a bus very early in the morning and arrive in Foz do Iguaçu at about 23h. A trip by bus of about 17 hours. It goes via Dourados and probably via Cascavel.
Try in Miranda to do the descend of the Rio Miranda until Passo do Lontra. You can manage it in about three or four days. It is possible to hire some little boats (voadeiras) in Miranda. This are boats that are normally hired for fishing but it is possible to hire it for some days and a driver (piloteiro) goes with you. It is possible to sleep on the border of the river. Take a little food with you for the days you will stay. Discuss the price. I did it twice when I was with a group of four. It was amazing. You cannot image what you will see during this descent.
Have a nice trip. and enjoy the Pantanal.