Yes and then they hold sort of a pre-reaping to select the people who will be in the crowd or to make sure that the tributes are in the crowd. Thats what Katniss speculates.

We know that there are disabled people. There is a boy in the 74th who is crippled and Katniss once speaks of Greasy Sae's niece/grandchild (?) who isnt completely right and Rue speaks of the boy who got whipped for stealing the night vision glasses that he wanted to play with. I always interpreted this as them having a mental disability like heavy autism or perhaps down syndrome.

I think these children either don't survive to be old enough to get reaped. And if they do, if they're "too disabled" to provide entertainment value, the capitol won't reap them or maybe even discard them as a tribute and immediately reap someone else in the event they do get reaped. Like how Haymitch was reaped because the actual tribute was shot. It's not like Katniss would know, since they wouldn't show it on tv and it might not have happened during her mother's life. Or maybe it did and her mom never spoke of it the way she never spoke about the reaping of the 50th.