Our kids are so excited about going away on summer vacation, they just keep putting stuff in and out of their bags.
この場合、次のように言えます。
ーOur kids are so excited about going away on summer vacation, they just keep putting stuff in and out of their bags because they're so worked up.
「子供たちは夏休みに旅行に行くことがとても楽しみで、大はしゃぎでカバンに（旅行に持って行く）物を出し入れしています」
to go away on summer vacation で「夏休みに旅行に行く」
to put stuff in and out of one's bags で「カバンに物を出し入れする」
to be so worked up 「大はしゃぎする」
ご参考まで！
So excited for a summer trip that they keep putting stuff in and out of their bags.
"夏の旅行が楽しみで持ってくものを出し入れして大はしゃぎ"
- So excited for a summer trip that they keep putting stuff in and out of their bags.
子どもたちは久しぶりの旅行に大興奮、楽しみ過ぎて、旅行に持って行くものを鞄に出し入れして大はしゃぎです。
- The kids are so excited to travel for the first time in a while. They are so excited that they keep putting the things that they want to bring in and out of their bags.
カナダ 
アメリカ合衆国 
