Just to clarify for those following: Cinderella's Castle and HEA are both in MK, at WDW. I don't know if either are being refurbed right now -- that would be something to check on the WDW board.
Sleeping Beauty's Castle is currently undergoing a refurbishment until at least March. No official end date has been announced yet. As previous posters have stated, Mickey's Mix Magic is the current nighttime show (viewed from the castle, Main Street, ROA, and IASW), with fireworks shown on certain nights. MMM has been running every night since Jan. 18th, even with the castle under wraps. And we saw the show from the castle the other night -- the projections and lasers are being shown on/from the castle just fine.
I thought the PP was getting confused, but the WDW MK fireworks show is HEA - Happily Ever After. And it is really good. MK fireworks finally caught up with DL's. And maybe surpassed it.
To the OP and a few others, first I am bummed when things are being refurbed. In the bigger picture, the issue of DLR and refurbs is well known. Jan-March (right after holiday season), along with September and to some degree October (right after summer season) are notorious for refurbs. For example, see:
"Choosing When To Visit DLR: Summary of High and Low Season and When Each Happens"
www.disboards.com/showthread.php?p=36509602
"What You Should Know About Off-Season at DLR"
www.disboards.com/showthread.php?p=18462889
WOC is an outlier and has been down since last April, and it is not a refurb.
When DLR has a refurb that is going to take longer than 3 months, they almost always will do it starting in January, and Spring Break is the peak season that is most likely to be affected by refurbs. Again this is well known and anyone can find this out who bothers to do just a little research.
We still do not know if Fantasmic or SB's castle will open for Spring Break. My guess is they will, or at least for the April part of Spring Break. If not, then that is disappointing. Nevertheless, DL's Fantasmic is not like WDW's and has it's own stadium. It is in DL and on the ROA. It went down for like
2 years when Disney was re-routing the ROA to build Star Wars Land just a couple years ago. Any work on the River means F! goes down.
Again, there is nothing super out of the ordinary here except for WOC. The knowledge shared in my links above is extremely clear, with dates provided, of when to plan your DLR visit to avoid refurbs.
I wish anyone going during this time to have the best visit possible.