(this is how I explained it to the students, btw. Though with easier English, of course):
1) The ALT and the JTE choose items from the list and place them in the picture. They should have different choices.
2) In groups (ideally 4-5 students/ea.) students will try to guess the location of things in the JTE and ALT's parks.
3) There are six locations corresponding with the six fill-in-the-blank sentences for each round.
4) One student per group will come to the JTE or ALT and ask them ONE question about the park (ex: "Is there a newspaper on the bench?"). JTE/ALT answers "Yes there is/are." or "No there isn't\aren't."*
5) Student reports back to the group (filling in the blank if they found an item) and the next student comes up and asks a question, continuing like this until they've correctly placed all six things in the park or until 10 minutes have passed. When I tried it with my lower-level class only one or two groups could finish in ten minutes.
this is the point in the explanation where you make groups and have them play janken to decide the order of students.
6) Have half the groups asking the JTE and half the groups asking the ALT. When Round 1 is finished, check which groups found the most items and award points, stickers, applause, etc.
7) Have them change who they ask for Round 2. Switch again if you have time to do Round 3 (though of course, the ALT and JTE should change their choices).
*Mention that they can ask if something is "in the park" first, otherwise some groups will, for example, waste four questions asking if there's an onigiri in a specific spot when there wasn't an onigiri in the park in the first place. If you want to speed things up, you could add that if they ask "Is there/Are there....in the park?" and the answer is yes, they can ask a follow-up question to ask about the thing's location.
Because it can take students a while to figure it all out, you might encourage them to eavesdrop on the other groups' questions. I once had three students, standing in line right next to each other, ask me the same question because they didn't listen to what the student before them had asked.
I found this used a surprisingly long amount of time and was good practice for lower-level students (the school where I used this splits the second-years into "advanced" and "standard" English, and this was for the standard class.)
You could probably adapt this so students ask each other, but I felt like having them ask the JTE/ALT ensured that they're actually speaking and that they're using the grammar correctly.