so it's difficult for us to find the time to let the younger two do the things they want to do.
Our daily lives revolve around the eldest child's (またはdaughter's) schedule
「いつもいつも7歳のお姉ちゃんのリズムに合わせての生活」= Our daily lives revolve around the eldest child's (またはdaughter's) schedule
「なかなか下の子達に合わせてあげられない」= so it's difficult for us to find the time to let the younger two do the things they want to do.
ボキャブラリー
daily lives = 日常生活
revolve around = 中心に回っている
eldest child/daughter = 長女
difficult = 難しい、しにくい
time = 時間
let = させる、やらせる
younger two = 下の子たち
do the things they want to do = やりたい事をする