Fields in forms:
You’ll need a third table linked to the other two, and base your form on that table. For your specific case, you mention “Families” and “Kids”, and I’d probably name the third table “Registrations”. Note that you won’t be able to filter entries based on linked fields, e.g. you won’t be able to select a family and only have kids from that family show up for selection. You’ll also run into privacy issues if you use such a form for registration because everyone will be able to access at least the names of every record linked to the table/form.
Airtable allows you to group records (e.g. by family), and you can get totals for each group.
There are a few solutions available (search the forums; they vary in complexity/cost).
There is a print layout designer, but for your purposes, you can probably just filter and print the various tables in your database.
The problem right now is that Airtable presents certain barriers: no data validation (e.g. phone number/address formats), no duplicate detection, and the aforementioned inability to filter linked records based on given criteria.
For me, I’d say the biggest hurdle you have to clear is the registration form. My recommendation is that you collect personal information first, assign each child a unique ID number, and then let them register using that ID number.
If I were you, I’d also check out another service, Fieldbook. Their formula syntax is a bit wonky (not Excel-like at all), but a bit more powerful. The interface is also a bit slower when processing large amounts of data.
However, the main benefit is that when you expand a record, it automatically gives you the full details of every record associated to it (in Airtable, you’d have to click into each records separately) – super useful if you want to print info sheets for parents about the courses that their children are registered for, since it’ll automatically include things like instructor names and locations (or whatever data you provide).
And it makes much better use of the screen space available to it (it’s relatively bare-bones when it comes to visual flair).
But Airtable is much more mature and stable, and also has a functional calendar view, which is the main reason my organization uses it. Since it sounds like you already have a few spreadsheets’ worth of data, I’d load them up and see which service works better for you.