All of you are in Adjustee status (i.e. 485 pending). So there is no fear of losing status. EAD gives authorization to accept employment.
If you (primary applicant) start to use EAD, then you and all your dependents have to use AP (advance Parole - Form I131) to travel in and out of US.
Cost wise , AP is cheaper, if we take into account the 1000+ $ fee for H1. But AP is generally valid for only one year, so you have to keep getting one per year (for each of the applicants). If you are in TSC, it might run >1000$ (4 applicants X $110 X 3 years)
EAD gives you freedom to chose your employer after 6 months of pending 485.