I would love any suggestions for how to help a 90+ year old man who is at home, who is losing his sight and his hearing?

What a sad situation! Bumping up your question.

My mother has both those issues. (Curses on macular degeneration!!)

He is going to be extremely isolated and get very withdrawn. My mom eventually refused to go out or see friends, and I'm convinced that contributed to her dementia, too. It didn't help that before her vision went she ran a library, read six books a week, and was an artist. She lost every activity she cherished.

If he can live in an assisted living facility, he'd have activities and people around that would help keep him mentally stimulated. Otherwise, it's so hard for them to do anything.

Contact the Braille Institute, too, for resources. He can get talking books through the Library of Congress for free, and they even send you a player to use. It's very archaic and clunky, but that's fine when you can't see a screen to swipe this way or that to turn the thing on.

Also, if he can still read somewhat, he could invest in a magnifying reader. My mother had a Merlin reading machine and that saved her sanity for several years. It can make printed letters up to about 2" high -- much bigger than a computer screen can do. They aren't cheap, but they can often be purchased used.

Just don't let him become isolated -- that's the most heartbreaking part of it.

https://www.enhancedvision.com/

Hello, My 87 year old mother is in the same situation. I am with her as her live in caregiver but she was always a private individual who loved to read. Here is what I did. We have setup Echo dots with speakers around the house. Light switches are hard to see and appliances that are hard to switch on were automated. Fairly simple with a series of smart plugs and bulbs. She can turn them on/off by voice command and via timings set through app. As for entertainment, I purchased a Kindle Fire 10 which has a large surface screen. We signed up for Amazon Kindle Books, Audible.com, Great Courses, and Great Courses Plus. She entertains herself during the day using kindle. If she wants to read she uses e-books and adjusts font to very very large. She can use kindle to launch audio books she enjoys and Great Courses which come both in audio form or audio and video. She's been learning everything from Native American Culture to Physics (she was a math teacher for 30 years). She can also engage the audible apps through the Alexa assistant on echo.dots in every room without the kindle. The echo.dots can also answer time if day, set timers for cooking, answer questions and even play trivia games.

For reading, I purchased several jewelers and electrician task lights with adjustable arms. Her dining room table is setup for her to attempt to read newspapers (can do this online as well through kindle). The task lights provide a large amount of light which can be brought right to page (necessary for Mac Degen). I also purchased a large print bible. She no longer attends church, but she joined Catholic TV and watched and listens to services on EWTN network. We also bought large print crossword puzzles and word games. Research Low Vision we sights for aids.
Along with the echo dots I got her a talking pendant watch. Large button. Tells her Time, date, Day.

For exercise, I purchased a Rollator European style (looks less like a walker). Macular people begin to always look down and shuffle while walking for fear of falling or tripping. The Rollator gives her support and confidence to walk with head up without fear of falling as it leads the way. Has breaks and a seat and a water bottle carrier. She loves it. We bring it everywhere. Even brought it with us on a trip to Florida. Rolls right to door of plane. I also bought her a small flat meant for under desk treadmill with a very slow speed and manual settings and handrail for winter. She loves that too. Along with those we got her some hand weights and therebands for light stretching exercises.
Aroundvtge house, I setup tactile things for her. Orange bands of tape at top and bottom of railings for stairs. Wrapped several rubber bands around as well, helps her to see and feel ends of railings. I also place mats at bottom of stairs so she can feel difference with her feet. Helps with possible stair falls.
For kitchen and appliances like microwaves, I have tactile soft, raised buttons that I put on significant digital press buttons like start on microwave. It helps her to feel which button to press. I purchasd large sticker microwave and keyboard letters, numbers, words and symbols. Cam get them on Amazon. Turns tiny numbers and letters in to large font bold.
Lots more ideas can be found on Macular Degeneration and low vision sites. Just think about your father's day to day routines (important for elderly helps them feel still in control of their lives) and see what you can do or replace to make the task easier. Work with them using new things like echo dots. Once they repeatedly use, they get the hang of it and you will see them doing it on their own. Good Luck.