A Medrash tells us that one Shabbat afternoon the two sons of Rabbi Meir and his wife Bruria died suddenly. She left them in their beds and covered them over with a sheet. At the end of Shabbat when Rabbi Meir came home he asked, “ where are my two sons?” She told them they went to the Beit Midrash (study hall) and that they would soon be coming home. She gave him food and after he ate she said she wanted to ask him a question. 'Yesterday a man came and gave me something to watch for him. Now he’s coming to take it back. Should I give it to him or not?' 'Of course', he said, 'you must return it'. She took him by the hand to the room where their two sons lay, and took off the sheet. When he saw their sons lying in front of them he began to cry. Bruriah said 'what happened here is just like you have me. We were given them to hold for a short time and now we have to give back the precious items to its owners'.
The parable is told of a king who had a precious stone that somehow had its surface indelibly scratched. The king was beside himself and called his trusted friend asking him what can be done to fix the stone. His friend said 'I can't repair it, but give it to me, perhaps I can do something with it.' He took the precious stone and using the scratch as a base carved a beautiful, many petaled rose on its surface. Returning it to the king he said, 'while I can’t repair the loss, I tried to make it a foundation for something else beautiful.'
Your friends and co-workers are reaching out to you to express to you that they stand together and empathize with you. My suggestion is to tell them your great appreciation for their donations, and to use those funds for a holy and charitable purpose, perhaps something associated with young people in need, or, if there are sufficient funds to establish a permanent foundation as a memorial to your dear son.
Words of consolation are inadequate at this time and your friends are attempting to show their support with the floral gifts. Perhaps these tributes can be a foundation for a charitable cause in his memory. I would suggest telling one of the co-workers the the Jewish custom is not to have flowers at the funeral. If they nonetheless come, acknowledge them and share them with an old-age home or with a retirement community. A floral tribute or bouquet can help cheer up the day for a shut-in or hospital patient.
I pray that you should be able to find comfort soon and have beauty of his life continue with good deeds done for others in his memory.