It's so good to hear that you and your husband are planning a trip to our little island!
Regarding the weather here on the Emerald Isle, it's actually quite temperate! As an island, there aren't really drastic weather changes, particularly over the span of just a few weeks. That said, we do have a lovely article right on our website that's all about planning for the weather
while here. There is a bit of a temperature difference expected between September and October, of about 5 degrees Fahrenheit, which may play into your plans.
In regards to things to do, there's plenty to do at both of these times! In fact, if you do pop by in late October, you will be just in time for the Púca Festival
If you'd like to learn more, there's a helpful article
that covers many of the big festivals and activities here in Ireland! Just set the dates you intend to visit, and it'll list any attractions that are open during that time. I'm sure it'll be a huge help!
If you need more help or would just like to chat about your visit, please feel free to stop by again! I'd love to hear from you, and I'm sure others here would too!