Here are a few things I like to do...
This is a fun math activity to introduce the idea of area and perimeter. We don't really teach area in second grade, but I like them to understand what it is because it will be a skill in third grade. This activity using candy hearts (or any other small candy) is a good introduction using non-standard units.
Here's another math activity using candy hearts. Students arrange them in an array. This is where I introduce the idea of multiplication. I have them write down how many hearts are in each row. Then, they do repeated addition to find the total. I have them hide their answers and let them take turns telling me how many rows and how many columns they have. They are always amazed that I can immediately tell them how many hearts they have. It's gets them excited to learn multiplication.
I also do Valentine heart graphing, addition, and estimation activities, Valentine's Day letter writing, abc order, and a fun word search. All of those activities can be found in my Valentine's Day Mini Pack: