At home would be better.
Adding young chicks is safer in re: disease because they've had less time to be exposed to anything dangerous. Especially day-olds.
I personally would add chicks on the principle of cycling ages to keep egg production up. But I don't know if you consider your chickens pets or livestock, if you intend to cull after a time, or what other management factors you would want to consider in your situation.
What's more available to...
I would not plan on them roosting together right off. Roosting is often the most contentious time of the day.
If you have space inside a secure run, this is the integration pen I used last year...
Welcome to BYC. Where, in general, are you? Climate matters.
Here are some useful articles on integration:
https://www.backyardchickens.com/articles/integrating-new-birds-at-4-weeks-old.72603/
https://www.backyardchickens.com/articles/my-coop-brooder-and-integration.74591/...