Some random thoughts, definitely not the final ones on our travels:
Don't leave your gondola ride to the last day of your vacation, because it might be rainy and cold and you might be too tired and the gondola will remain unchecked on your bucket list.
Make suggestions, but don't set anything in stone.
If you have more time, try to get out of the cities and into the countryside because it looked really beautiful from the train windows.
Ask for help. The Italians we met all bent over backwards to help us, from joyfully assisting my mother navigate the inaccessible to calling a giant taxi to get us and all our luggage plus a walker and a broken wheelchair to the train station. We owe them all a big thank you.
And if you try to avoid a time when it might be crowded, like Easter in Rome, make sure that you don't accidentally arrive instead during a time when it might be even more crowded, like the never-before, maybe never-again, canonization of two very popular Popes. Three million people in Rome had an effect.
But most of all, go! Do the best planning you can, deal with the broken wheelchairs and millions of people, and have a memorable time!