Rainforest is on the opposite end of DTD than Cirque du Soleil. Good news is as long as it isn't raining or thundering and lightening, you can take the ferry from the dock next to the Rainforest Cafe to the dock behind House of Blues. You will make an intermediate stop at Saratoga Springs on the way.
You will have to call Rainforest Cafe directly to make PS arrangements. Disney Dining does not handle that for them.
Cirque du Soleil asks guests to arrive 30 minutes early, as there is a preshow that begins at 8:45 pm. I would think if you ate at 6:00 or 6:15, you would be fine to get to the theatre by 8:30 to be seated.