Depending on where you are going, some areas are SPREAD OUT, with a connected cell phone it is amazingly simple to plan such a trip. Google maps alone will allow you to do a lot of the planning. And this is before we talk about all the mapping/navigation software available to determine elevation gains and availability of bike paths and quiet, scenic roads, etc.
And don't be afraid to do short rides each day; 10 or 20 miles (or more) a day is totally fine to do. Don't be seduced/shamed by these epic Herculean tales of 70 and 100 mile days done by folks at the peak of their youth and/or strength and vigor (though they have their place).
There will be immense satisfaction rolling 20 miles down the road, having a casual lunch, checking into the motel or campground, getting situated, and then regrouping at a communal area and having a nice cocktail. And then striking up a conversation with whoever happens to be there.
This is called Type 1 fun. The idea is to keep it light and fun; low stress. Sometimes this is underrated.