I would definitely recommend Lexis Hibiscus at Port Dickson! They have "Kidz World" - children playground, costs 20RM for a 1 hour entry, and they have additional activities there (at additional costs). They also have an outdoor kids pool and playground (next to the pool)! Also, every room has a private pool so that is nice for the parents (and the rooms are aesthetically pleasing) :P Other than Hibiscus, you can also consider Grand Lexis Resort - cheaper, also has a private pool in each room & children's pool :)
There are many good options to choose from for families at Port Dickson. You can try Avillion Port Dickson, Grand Lexis Port Dickson or Port Dickson Golf & Country Club. They have good amenities and are not very pricey too!
Hey, if you are looking for a budget friendly resort, Glory Beach resort is pretty decent, and staff are friendly , and service is quick too.