Why not: Are they good things?
The meaning is literally exactly the same as the answer you have in English. I can't think of a context when the sentences would have different meanings.
I believe that your sentence would be "Jsou TO dobré věci," where "to" is a pronoun standing in for "they" or "those," rather than a modifier of "věci." Here, "ty" is a modifier attached to the "věci." (I hope that makes sense...)
This is not a sentence that would ever be used in English is it? If I meet someone I could ask them "how are things?" or "are things good with you and the family?". I'd even drop the "are". But I'd never ever say "are the things good?". Not that it matters really, I guess this is a Czech course, not English haha. But do you use this sentence in Czech in the way I wrote it in English, as a way of asking how someone is doing? thanks