That was going to be my advice too! Rent a double stroller...let the 5 yo ride...one of the older kids if they get tired and plus you'll have space for your bag. Bring something to mark your stroller (we use a bright hankie).
Have the kids wear the same bright color (if possible) that way it is easy for you to spot them all. You can wear the same color too, easy for them to spot you.
For my kids, I went to Wal Mart and had those pet tags made up with their first name and my cell phone number. I attached the tags to their shoestrings. Turned upset down, a stranger couldn't see it but the kids knew to show a cast member. That way if they are lost, I can be contacted. I instructed both of them what to look for in a cast member so they could find the right person to help them if they got lost.
Every day everyone got to pick a favorite thing to do, then the rest fell into place.
Snacks and a water bottle are great waiting in line things. So are bubbles, really great!
Use fast pass.
Use the photo pass, as much as possible then have your pictures put onto a CD.
For you....try and remember there will be meltdowns (kids and yours). Breaks will help that. Even if it's only porch sitting somewhere.
Last, you could take me with you and I'd gladly help with the kids
