From the photos it looks like your Mum already has many lovely pieces. Perhaps you could have a girls' day shopping and choose something together which would have special meaning to her. Or else go for something different and treat her to a day of pampering at a beauty clinic - massage, manicure, pedicure, facial - the list goes on. Olivia, I'm sure she will love whatever you do.

Here's the pic from there, why do you want it? I'm wondering if the extra corner might be a trip hazard

you used to be able to buy Minwax at Masters when they were around I would try Mitre 10 I used it on another property and it was excellent

Your question has appeared on the Australian Houzz site. I sympathise about your clay soil. I live in a region with heavy clay soil and brought in special lawn soil for the lawn area. This is the US site https://www.houzz.com  Houzz now also owns Gardenweb which has a specific Lawn Care forum where you should be able to get help with your question. You can find it by going to Stories & Advice at the top of your screen and clicking on Gardenweb Discussions and then going to Explore Topics on the left side of your screen and clicking on Garden Forums where you will see Lawn Care listed. Here is the direct link. https://www.gardenweb.com/discussions/lawns