Sounds like a honey do list that is rather fun than just chores.
Lowering links are not a terrible thing if the job is done right. If you adjust the rear height, then also make the relative change in the front to keep the bikes geometry and balance the same. And since you're there, do your best to set the suspension up to best suit the rider and you will improve the bike overall, despite it being lower.
As far as the seat goes, imho shaving it is the best route. Not only for height, but also for width and angle. For my short wife, shaving the width was the ticket!
Levers.. get some folding ones. The2Wheels levers from ebay are a popular and very cheap lever that is fairly adjustable but the plastic perch will break easily in a drop or fall. The folding levers will allow for less chance of breaking the perch but ymmv ya know... each down is different.
I can't help ya with sliders, never ran any and don't plan too.
Oh! And gratz to your wife on her new ride.