I'm happy to hear that you are planning a trip to Ireland next month. I hope you have a great time.
A reservation is not required in order to visit a pub though I would point out that this may vary from pub to pub.
To access indoor service, you must show proof that you are fully vaccinated or have recovered from COVID-19 in the past 6 months. Children under 18 who are dining with you do not need proof of vaccination or recovery. You may be asked for proof that your child is under 18. Click here
to learn more about the current restrictions in Ireland.
Please note that the Irish government is planning to lift a number of current restrictions on 22nd October, which may affect your trip depending on the dates. Check out these plans to lift restrictions on this date here
I would also recommend that you keep an eye on the Traveller Health page
for the latest travel advice and restrictions.