Getting a puppy with my 2 older cats?

So I currently have two 18 year old cats, male and female. They can go inside and outside, whereas the puppy would only be allowed downstairs. So my question is, would the puppy stress out my cats or would they be fine? They spend most of their time upstairs sleeping. The puppy would either be in their crate or play pen unless supervised. There will be someone at home most of the time. Thanks!