I set up a spreadsheet in Excel with two worksheets. The first worksheet is for the cost of the holiday, the second is the planner.
When I'm pricing up different options (eg DIY or package, flydrive or flight only, etc) I find it much easier to lay it all out in a spreadsheet so calculating the total cost is done automatically. Saves lots of work with the calculator.
The planner could just as easily be laid out using tables in a word processor but I find it easier to keep it in the same document with the costs. All I do is to record park opening times, parades and fireworks, any PS reservations and hard tickets such as Discovery Cove. This all gets printed out on one side of A4 and is a useful summary of all the planning info we need. We don't plan our holiday day by day, prefering to 'go with the flow', but it is useful to see at a glance what all the opening times are.
Regards
Rob