I've been doing the envelope method for years, and it works perfectly!
I do a food shopping envelope, each day we are there, souvies, mousekeeping and tip envelopes. Every night I "reset" the backpack for the next day, removing the envelope and it's contents and putting the new envelope in it's place. I take out the $5 mousekeeping and put it on the bedside table so I won't forget, too.
I save all the time for whatever Disney adventure is coming up next, and convert money to TC as it's saved, so it's as safe in my house as it will be at WDW! The only envelopes that have actual cash in them are food shopping, tips, and first and last days (travelling).
Whatever is left when we leave is paid on the rental car (the only thing I can't pre-pay). One year I had $342 left from all of the envelopes, so my rental car was paid cash when it was turned in. My goal is to charge little or nothing every trip.