My son has a lawn care business, and it has grown, becoming hard to manage. He wants to get a tablet with an app to "help keep things straight."

I have categorized the hard-to-track areas into three general groups:

This is not exactly 'schedule' data as each event (house) is not at a particular date or is a sequence of steps, usually beginning on a Monday (sometimes not if rained out). Often, WHAT is to be done at some stops is changed ("next week, will you trim shrubs please"). So, while routes are SOMEWHAT static, there are constant adjustments, usually of a one-time nature. Must show WHAT is to be done at each house routinely too.

Some things ARE "do THIS at THIS time on THIS date."

-TO_DO items. These are not repetitive, not exact-time items, but often do have either a priority, or a do-before-xxx constraint.

Also, he cannot spend huge amounts of time manipulating data, so ease of use is important.
I recognize the above is a very tall order, but I am looking to help him find a solution (app) that best assists him to keep track of everything.

Does anyone have any ideas?