The goal of this activity is that kids tell others their plans (or wishes) for summer vacation.
I've added "if" in order to connect another grammar point. That way it will sound more natural, and the kids can also understand how to use it in a natural context.
First, make a small presentation (easy, simple, and straight forward) about your plans or wishes for summer vacation.
"If I have time, I want to go to Yamagata. I want to eat cherries there. I want to go to the beach, and swim in the ocean. I want to eat great sushi too."
This is very easy, and they can do it without help pretty much. Don't give them scripts, and don't ask them to write anything. This is a speaking activity. Teachers will tell you that it is too hard. Yes, it will always be hard if kids don't practice. It is a learning process. So far, this is elementary school grammar.
Give them 2 min, so they can think what they want to do during summer break. Tell your kids to think what they want to do in the place they have chosen. This is crucial for later!
Make pairs, and let them do janken. Winner goes first. When the winner is done, the partner will do the same thing.
Do it this 2 or 3 times until they feel confortable. You can point few kids, and see if they are doing it correctly.
Now comes the crucial moment. Tell your kids your plans again, but now add the infinitive form:
"If I have time, I want to go to Yamagata to eat cherries there. I want to go to the beach to swim in the ocean, and to eat great sushi too."
Give them time to see the difference, and ask them what's new. I'm sure, someone will say it in Japanese. Once they understand the new grammar point, they can make pairs again, and talk about their plans for summer vacation using the infinitive form.
I give them a worksheet at the end of the lesson (last 5 or 10 min) to write their plans for summer. If they don't have time to finish, don't worry. If they write just one sentence you should be happy. The important thing is that they know how to use the grammar point.
Hope you like it!