First of all i am a fan of your approach, 8 tiles linear navigation i envy the simplicity.
Second I have to clear-out my responsibility to this question as you have not indicated the purpose of the tiles, i am assuming those tiles provide nice informative value such as the weather and such, so nothing of high impact like emergency calls or health related information etc...
One technique you can consider is a better global order through analytics, statistically whats the most-least frequent tiles your users use, with this one you can benefit with one of two ways:
The obvious one
Most frequent on the top to least frequent on the bottom of the list, this one causes your users to easily access the most frequent tiles.
The dangerous one
You could go with a crazy idea that is the absolute contrary of your original proposal:
Least frequent on the top to most frequent on the bottom of the list - controversial but hear me out first.
The disadvantages of "The obvious one" comes with hiding the less frequent tiles, meaning the user might not realize their existence or simply forget about them.
This way you would ensure that the user will use the scroll frequently and occasionally notice what is provided while scrolling down, therefore not missing out since you have just established a frequent behavior.
I have to make a disclaimer here though, do not mess with the seniors you better be knowing what you are doing before you commit to this one, so keep in mind it wouldn't work for example with non-frequent users or users with memory struggles, but now comes the real question:
Why do you need to change things?
Do you have a good reason to do so? The way i see it, it's not a huge content platform it's 8 tiles, the most successful scenario for your sorting is bringing tile #8 to #1 is it really needed? Are your users struggling with finding the tiles under the screen or you just want to make things more reachable?
If it's the 2nd answer then you really don't need to, i don't have much work experience with seniors but i have in my life and from there i can safely say it's much harder for seniors to learn and adapt to change, rules, and concepts (such as sorting, or how the sorting works etc...) than learning things as is or as steps as you have mentioned (navigate down, you find tile 8).
If the users are indeed struggling with the findability and reachability of the tiles, there are things you can do let's break things down a bit:
Change order by relevance
- Yes, we can introduce manual ordering (requires learning, increases interaction space)
- Yes, we can introduce automatic ordering (confusion & complexity)
Is it possible to show all of the tiles in a single view?
- Yes, we can reduce the content size (create accessibility issues)
- Yes, we can eliminate some of the tiles content (reduce added value)
- Yes, we can eliminate some of the tiles themselves (defeat main value)
- Yes, we can introduce hierarchical navigation (confusion & complexity)
So as i'm sure we all know there will always be a compromise somewhere i just felt the need to highlight some, of course depending on your budget you can experiment and if you decide to do so i would recommend that you perform user A/B test with on the current and the new solution.
Again, my final advice would be not to change the order unless you really must