Welcome to the community!
There are a couple of ways to approach what I believe you want to accomplish.
Your single most significant limiting factor in what you’ve described is the usage of the multiple-select field.
With your current data structure, you’ll probably want to rely on the Summary, Pivot Chart, or Chart extensions to provide you with a quick, high-level glance at your data.
For what you’re looking to do, I would recommend you make a few tweaks to your data structure.
Here’s how I might approach your use case…
I created a demo base for this post. If you’re curious to poke around for yourself, here’s a link to it.
Feel free to duplicate the base into your workspace and use it if you’d like
From what you wrote, you have two simple types of data: the children attending, as well as the actual weeks themselves.
This means that we’d want two separate tables for our data.
I’m a bit bored tonight, so here’s an example I built:
The attendee data is programmatically generated.
I went ahead and generated 100 random records.
Then, I created a linked record field between the Attendees and the Camp Weeks tables.
From there, I went ahead and linked a random number of attendees to the different weeks.
That ends up looking like this:
It’s kinda ugly as is, so we can use lookups, counts, and rollups to format our data to a more readable format.
Using a rollup field, I can summarize how many attendees are signed up for a single week:
Now that we have this structure built, we can also start to account for scenarios where an attendee might be going for multiple weeks.
This schema design allows me to summarize more specific data points such as how many attendees are signed up for multiple weeks.
There is some cool stuff you can do once your data model has a strong foundation.
It’s really up to you at that point.