You may get your answer at a Pre event Tech Inspection. They check things like tires, brake pads, wheel bearings etc. If they tell you your tires are a no-go, you will have your answer, won't you
You would be happier on your existing (used) tires. The most "wear" you will likely see is not tread wear but "shoulder" wear as the front tires take the abuses of cornering. The smaller the tread block, the less "chunking" your tires will show. That said, since you know they are wearing thin, if you can still see the tread wear indicators, you should be ok.