Annuals like petunias are a great way to get them involved. They are easy to grow in containers and low maintenance and if they like veggies find out what their favorites are. There are quite a few that do great in containers. For example, you can now grow big slicing tomatoes on small compact plants.
The biggest advantage to using annuals and/or veggies in pots is that they are lower maintenance and there are no worries about bringing anything in to overwinter. Just put new soil in the next season and new plants.
