yes they are going every night at both parks, unless they don't show them for some weird reason. The only thing is if you are going at an off time, the times for the fireworks will be earlier than if you were going at a more peak time of year.
Also, starting last year, the nights of the special parties at MK (MNSSHP and MVMCP) fireworks are only shown during the party, not during regular park hours.