Yes for the dependants themselves: L-2 spouses are employment-authorized incident to status and children may study. The difference between L-1A and L-1B lies in the principal's ceiling and evidence, not the family terms.
Family terms follow L status, not the sub-category
Hypothetical example: A household comparing an L-1A and an L-1B possibility should not weigh them on spousal work, because the position is the same: a spouse in L-2 status is employment-authorized incident to status, and children in L-2 may attend school but cannot work. What differs is duration. L-1B is capped at five years while L-1A extends to seven, and for a family planning around school stages that gap can matter more than anything else in the comparison.
A Selwyn household should therefore map the children's ages and school transitions against the ceiling that applies to the actual role, not to the more generous one. If the plan depends on remaining beyond the applicable limit, the route out of that ceiling needs to be identified at the start rather than assumed to appear.