Etiquette sides with restingdonkey's side. Asking for money in an invite is traditionally a big no-no. Spreading the info via word of mouth is a good alternative. Another thing to point out is that shower's aren't planned by the bride and groom. They are done by friends and family. I understand that circumstances may exist that make this not the case, but someone you know my be planning a shower without your knowledge. Especially with a year to go, you might have a change of plans (even unannounced to you
).
Good luck!