We are considering a trip in early March. Trying to choose dates. Would fireworks and night shows be weekends only? Any other advice for that time of year?
It depends on when in March you are going. If they follow the pattern from 2017, then they do present fireworks (and possibly F!, it hadn't re-open yet) nightly once they've moved into their Spring Break season schedule. This year, it started on March 24 and ran through the week after Easter. In 2018, Easter is going to be on April 1, so they might start the nightly entertainment schedule earlier in March, but we won't know for sure until they post the operating calendar (starting about 45-days in advance).
Some of the DTD locations have participated in the past. It's not a big event (from what I can tell and doesn't have much (if any) impact on DLR). Basically, participating restaurants usually offer some kind of special prix fixe menu during that week.
If you're going that early in the month, then I would plan on having a weekend (Fri-Sun) if you know you want to see fireworks and/or F!.
The Natural Products Expo is a large convention. It won't necessarily have a big impacts on the parks, but it can really impact the hotels/motels in the area. So make sure to make your reservations early.
With your planned dates, I would include at least one weekend day if you are interested in fireworks and/or Fantasmic. My guess is that fireworks will only be weekends. I don't know if Fantasmic would be nightly. World of Color would probably be nightly if it's not down for refurb. Be aware though that fireworks do get cancelled if it is too windy, so even with good planning it's still possible to miss out.
Usually weekend nights mean Fri, Sat, and Sun, but as longtimedisneylurker mentioned, fireworks can (and often are) cancelled due to weather (usually wind at higher elevations). So it's best to have a back up night planned.
Following cause we're looking at an early March trip too - probably the very first weekend. That Sat is mini gay days though, which I'm hesitant about cause of crowds. I can't decide if we should do Sat at all or not! I do love the longer hours of the weekends!
Was also thinking of the weekend you're looking at...
Let us know what you decide!