Welcome to the Disney Parks Moms Panel, Karen, and thank you for stopping by with your question! Your trip is just days away, how excited you must be! Yay!
Hot water is so helpful to have at times, especially when traveling with little ones. Personally, I have asked for hot water at quick service locations and sit-down restaurants several times and they have always given me some at no cost.
I just checked with
Guest Services and they said that it would depend whether the specific dining location has the resources available to provide it to you and do so safely. If they do, they should be able to give it to you, so it doesn't hurt to ask.
Remember to always be extra careful when handling hot water and to use a lid whenever possible; water that comes out of those big dispensers tends to be several degrees above what we would call hot.
Karen, I hope this has helped a bit. I hope you have a truly magical vacation!
See you real soon!
~Desiree