Recommendations needed for 2 open days in March- 3 younger kids

[DMA832]

From March 18th - 27th - We will be spending 5 days at DL/DCA, 1 pool day (if it's warm enough at the DL hotel and have two open days at the beginning of the trip. I have three kids - 6, 4, and 2. I've been doing research but would love some recommendations for those two open days We were thinking of going to a beach, possibly Manhattan or Doheny State beach and/or La Brea Tarpits (4 and 2 yr old are obsessed with dinos). We are open to staying in a hotel close to whatever we decide to do.