Transportation timing from Universal to POR - Help!

We are going to Universal for two of our five day trip, and Disney the other three days, with one caveat. On April 9th, we are going to our second day of Universal, but have dinner reservations at TRex in DS at 7pm. My DH’s actual birthday is April 8th, but this is the restaurant he picked for his Birthday dinner. hah.

We were hoping to go back to POR, either shower or nap (adults shower, DD7 nap, at the least), and then go to DS for dinner. We don’t have to arrive early and shop, but we wouldn’t be opposed to doing so.

What time should we leave Universal (We would be Lyfting or Ubering) to get back to the hotel, have time to relax for a bit, and then hop on the boat to DS? Crowd levels are around a steady 5 for the whole trip, so I am presuming we wouldn’t have to wait for more than 1 or 2 boats to have a space, but maybe that’s wrong thinking. I was thinking leaving Universal at 4 would be enough time but is that crazy? Should we leave at 3?