Note there are no Express Passes for anything in WWoHP. We found it very easy to drive from WDW to US/IOA. We used the valet parking (although I don't suggest the upcharge from that - there was no crowd when we left, so it did not get us our car any faster - and this was on a busy summer day).
The valet parking saves you some walking/moving sidewalks, but you still walk through CityWalk to get to the parks.