Walked across patch of grass to car in complex with kids when noticed a pesticide sign with pic of adult and kid walking dog with an x. should i worry?

Probably fine: If you walked across with shoes on and your children also had shoes on,and washed hands, it is likely not a problem.Would wash off shoes if haven't done so. Call Fair Lawn if this was a town field/rec area and they should be able to tell you what the pesticide is and when it was applied. These flags often get left in place for weeks; if that is the case,likely not a problem.