If you were having the wedding at a marriott, and they would take the credit card, and treat the charges as stay charges, you could get 600,000 marriott rewards points -- more than enough for 2 travel packages (240k miles and two 7-day hotel certs).

But, since it looks as though you're not doing it at a Marriott, I would think SPG is the best way to go, unless you have another card that offers bonuses of particular use for you. For example, with the USAir card, a 25k spend gets you 10k EQM and also other benefits (5,000 mile reduction on awards, etc.)