Requesting a charity contribution rather than a gift: It is very poor wedding invitation etiquette to even mention gifts but most invited guests will enquire if there is a wedding gift list. The other members of the wedding party should be encouraged to put the word around as to what the bride and groom would prefer.
What Type of Reception? _ You should also give an indication of what type of reception you will be having so that you guests will know what to expect food wise. So if you are planning on having a two hour cocktail party, it's a good idea to put a start and assumed finish times on the invitation; this way people will be expecting nibbles and not a full meal.