You will make your PS just fine using Disney transit if you are staying on site. You will only need to think about driving for an off-site hotel. Disney has been doing this a long time and they wil make sure that you can spend even more money with them, esp since you're right there on-site at VWL (nice spot too). If you're really nervous about it you can always walk it, but the boat will get you there right on time, don't worry.