You realize this functionality, assuming you get it to work, is useless if the report is mailed/printed? That's probably the main reason why it's uncommon to interact with reports this way. If you're going to say that he/she always will look at this via using the db, then I'm afraid your hesitation for not using a form makes no sense to me - especially when clicking this checkbox can record in a db table that it has been reviewed. Plus, it's easy to undo if someone changes their mind.
If you must have it as a report, then what I'm not seeing here is if you can get it to work by opening the subreport directly instead of trying to interact with the sub when the main report is open. If you can, then maybe a reference between the main report and sub is the issue, but I'm not getting a sense of that from your posts. 20 subreports on a report seems a bit excessive as well, but maybe that's not as uncommon as I think it is.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.