At EMPOWER they demoed you're approach. But that as just directional and won't be coming for a year.
so what we do Quick Base style is to create a Parent Record in a new table called Member Meetings. Set the key field to be hyphen delimited concatenation of the Record ID of the Meeting and the Member.
Make afield there called Member Meeting Exists? With a formula if true make a relationship back down to check in's with calculated reference fieldLook up that check box field and now you know if there is a parent. maintain the master table with an Automation initialize the master table off a summary report from checking
So yes quite a few steps and if you know what you're doing you can do it in about five minutes but at least you can know that QuickBase recognizes that it would be nice to do this without having to create a relationship and look up fields to make this happen