I took my camera (500D) and a couple of lenses to Orlando a few years ago, by day three I was fed up of carrying it, the family were fed up with me moaning about carrying it and I'm sure people were fed up with me hitting them with my camera bag at every turn (especially whilst queuing). One of my children also put their fizzy drink in my bag, which leaked, which meant I had to send the camera away for repair when I returned home.
For this year's holiday, I decided to leave my kit at home and buy a superzoom bridge camera. I went for the FujiFilm HS50-EXR at £260 inc VAT, it was half the price of the new lens that I had my eye on, but it weighs a lot less than my camera (let alone the lenses), has a 28mm-1000mm lens, panoramic and video (both HD and slow motion) functions built in, it shoots raw as well as fine jpg and I was genuinely surprised at the quality of the shots. My children seem to love using it, so they don't mind carrying it for a while. All in all I wish I'd taken this to Disney.
Whilst a superzoom perhaps won't produce the quality of images that your 5D would, I think you'll find it a lot more convenient as well as a lot lighter to take with you.