A wedding is never an emergency hence couples should always be ready for it, not only the common psychologically but also the rare financially. Asking for contribution to fund your wedding plans is not only a nuisance but also worse an insult. I urge people and more so couples to cut their cloths according to their sizes and stop asking financial help towards their weddings plans.
Moreover, the wedding is yours not your friends' the honeymoon too will be yours with your newly wedded partner not with your friends or relatives.
But when you decide to ask for the fundings, appreciate whatever is offered and avoid telling them that the amount they've offered is too little for you to accept.
If its a must that you must ask for contributions then there are ways in which you can do it and still sounds cool,
First, you can indirectly approach them on the issue. Sending a card is more pressuring and leaves one with no choice. Find a better way that doesn't feel offensive or forced.
You know them too well. Maybe you've been in a relationship for sometime now and this I think is what qualifies you to approach them with your financial challenges. It is therefore evident that you understand them too well and know the tips you can use to get the assistance from their pockets. Avoid telling them directly that its a wedding issue because this will look like an insult on yourself as the person in need.
Secondly, just trick them by asking them if they could wish to participate in your wedding plans. This sounds wiser and they'll find it difficult to ignore it. Trust me, with this, you'll never hit the wall. Am sure most people will prefer monetary support than any other form of assistance. In fact this sounds a better way of asking for assistance in your wedding plans .