I stand to be corrected but I am pretty sure that if you are just after the experience and knowledge and have no intention of a boaty career, then do a 5 day Coastal Skipper course which will deliver at its conclusion a crisp Coastal Skipper Course Completion Certificate.
You only need a first aid cert if you are taking the 2 day exam with an RYA examiner immediately afterwards to achieve the Coastal Skipper ticket.
If you do decide later that you want to do your Yachtmaster Offshore/Ocean exams, you can always do the 1 day First Aid course and take the Coastal Skipper exam.