Work - should I continue to coast or push for additional support?

Hi all I'm 37m, two young children, live in the UK and own a property with 8 years left on the mortgage. I'm a Partnerships Manager at work and been here for just over 5 years. Work is busy, very busy, especially as there was originally 3 people doing my role but redundancies and subsequent job consolidations has left me literally working across 3 different companies (part of the same group). I'm happy with my pay. Could get noticeably more moving but I'm not career ambitious. Though, as I will get on to next, I'm very busy at work, I enjoy the freedom and work life balance. Frankly, I can leave the office when I want, my boss doesn't micro manage me at all and only really cares that the commercial numbers are where they need to be. I'm good at my job, somewhat highly thought of, can pretty much coast and at least succeed target and do a lot more when I put some effort in. With that said, it's crazy busy. I'm in a senior role but because I don't have anyone underneath me, or even sit within a team that could help out, I always getting pulled away with minor things that need to be addressed. Could be a complaint or a URL not working etc. I literally negotiate million pound deals but then have to get a spelling mistake changed on site or on board a partner that will generate £100 a year. I have brought up hiring an additional person with my manager a few times but had a proper discussion last week as my work load just became too much and I found myself ignoring everything else but the big stuff, but the small stuff all started failing and causing numerous problems of their own. I've been told it's unlikely but something they will genuinely consider if I can draw up a business case for it. Now that the opportunity has been presented to me, I'm on two minds. 1. Push for an additional hire, split the work load and now be in a position to focus better on the bigger things, possibly get a promotion etc. 2. Suck it up and continue to do the bare minimum. Not having someone reporting in to me means I don't have to constantly be on call. I can leave the office when I want without it being noticed and don't have to be responsible for someone. I've always leant into the latter. My frustrations at work come from how having to deal with the small "crappy" stuff and bring stretched too far, but at the same time I'm not career ambitious. I could tolerate this for another 5 years. Will be frustrated, won't enjoy the job but at least I don't have many eyes on me. Thoughts?