I would talk to the family and see if they belong to a church or maybe the Father belonged to a church or was a Boy Scout or a part of an organization. Maybe talk to the Son about the Father and find out any activities or organizations he was in and that might be an idea to donate to that organization/group, if it was a big part of his life. If you can find that out, then you could send a donation that way. My Dad passed away last year and that's what my Mom did was requested no flowers and said to send money to her church for a children's playground or the public library.
Meals are nice and the family will really appreciate that too. Most people bring casseroles and bigger dishes for lunch/dinner. I would bring maybe donuts or some breakfast food-sausage/egg dish or some other dish like that. Croissants and jelly would be great or Krispy Kreme donuts,etc... Another thing is potted plants, those are nice rather than flower arrangements that die.
A lot of times in the obituary, you might try and get the name and look at the obituary; the family will make requests there. If you know where the visitation and funeral is, you could also call the funeral home and ask them.
Another idea is for several people at your work to go in together and get a bigger gift-platter or more meals or a bigger plant.