Creating a Cart with Limit

I am a photographer and many of my clients want to choose from different options for prints. Example 5 8×20 2 5×7 1 16×20

My basic idea is to have them
1. select a package from a few options.
2. That would then limit the items being added to the cart to just filling the package items.
3. Once package is filled they can add other images to their cart but will get a warning that they have reached the package option limit and any thing else added will be an additional price.

Hopefully that makes since. Any ideas or input are welcome.

Also in #PHP _↴