Pencils not posies: Bridal couples often receive flowers at their wedding. How about collecting, and donating, school materials instead?
In many countries it is customary for the bride and groom to be given flowers at the wedding. In Poland, for example, this often results in ridiculous mountains (truly) of flowers piled up at the church door. The expense is huge, the enjoyment is only fleeting and then the groom's friends have the problem of what to do with the mass of bouquets which have nowhere to go but straight to the dump.
How about collecting school materials and donating them to an underprivileged school or some other educational or care institution? It's practical, it's simple, it's local and it is easily achievable.
Ask your guests for pencils not posies. Find a school that needs help - there are plenty of those, unfortunately, regardless of where you live. Put on your invitation that you would specifically like to receive art materials, copy books, pens, rulers, and so on, instead of flowers, and watch what happens. Peoples' generosity will amaze you.
Then pile it all up and send it off to kids who need pencils a lot more than the rubbish dump needs a pile of rotting roses.