Before the planting event, prepare the planting area
If working with children especially, you will first want to loosen the soil in the planting area and perhaps add additional planting soil. It's important to make the soil loose for small hands to dig, and double check that you don't have a layer of hard clay below a thin layer of topsoil.
It's possible that you can do this activity in container gardens on an apartment balcony if you don't have access to a yard. To do that, you'll need to purchase some large containers and research best practices of container gardening. If you don't have a yard, you could also ask your local nature center or park if you could plant in a small bed there.
This is a great activity for a birthday party or as a family event. You can encourage each guest to bring a plant as their gift to the birthday person.
Also, if you are looking for inspiration, here are 16 tips for gardening with kids.