You can select “Show Summary on parent Item” in the date column menu, which will show a timeline Mirror column with the start - end timeline of subitem dates. This summary information can even be used in Gantt charts as a timeline.
You can use market place apps like Copy Paste Master to create board automations that allow item data to appear in text or number based subitem cells in a seamless way.
If you need any help with implementing either for these solutions, feel free to contact me via my site at alldayit.com, or pm me here.