We were in your exact situation a month ago. In the end we did cancel the Helios reservation and go with
dvc. If you do this you will have to pay to park at epic, but we really wanted the onsite hotel for the extra morning hour. In the end we just wanted the comfort of dvc instead of a single hotel room. It all worked out really well, and we didn’t miss the extra hour. We were plenty exhausted by the end of the day because it was a hot day! The lines were manageable. We only had two “long” waits. We waited at ministry for about 45 min. And the donkey Kong ride was over an hour. The Ministry wait is not bad at all because the line is mostly inside and the line itself is almost a ride, really cool. When I see what they did I am shocked at how relatively spartan the theming is for the lines for “new” Disney headliners like Ratatouille, Tron, and guardians. The DK line was rough though because it was outside and was a typical snake line. Overall though we were very pleased with wait times and are going again next month for a day while staying at dvc.
