“The appellant raises one legal issue on appeal: she contends that there was no material change in circumstance that would permit the motion judge to revisit the parenting schedule. We disagree. The motion judge found a material change on two bases: 1) that the children were 10 years older than they were at the time of the original order; and 2) that the children had been consistently asking for more time with the respondent. These amount to a material change in circumstance.”