We did Disneyland for DH's block leave before Iraq last year and drove so we took our Bob stroller and it was awesome. This year, we are headed to WDW in August (only option thanks to the Army) before Afghanistan and I believe that we definitely need a stroller. George is not a huge walker and will still be 4 when we go. Plus, the heat will tire him out easily.
The trick is that we're flying this time. We're doing a week in NC (where we fly into) with my parents and then driving down to FL for a week. I'm tempted to take the Bob again due to easy of use, storage, etc, but, because we're flying, DH says rent or take the Mac.