Why has Arlo always talked Janis out of having the perennial garden she wants? They require less work and water long-term.
There are native, drought tolerant, deer resistant and low maintenance, flowering trees and plants for every area that look good every season. These also help butterflies, bees and hummingbirds.
Build some shade structures and they can enjoy sitting outside in the summer heat more. Add drip irrigation and mulch and it’s even easier to care for.
Get advice from your county gardner’s groups. Ask Gene, Mary Lou and Meg to help with labor. Or hire people. Arlo doesn’t even have to do the work if that’s his concern.
I’ve designed and helped build gardens like this for friends and family all across the country.
It’s totally doable, would make Janis happy, and is easier to maintain as they get older. No reason not to help her create this.