Ask the hotel whether they accept IHG/Crowne Plaza gift cards for the catering. I saved my parents a boatload for a wedding they did at a Marriott a few years ago. Check the various cashback portals (we used Topcashback.com, which at the time was offering 15% back on Marriott purchases (including gift cards) and Marriott had a nice promo going on for gift cards that stacked). Ended up being a total of about 23% cash back off of their negotiated rate at the hotel, plus 2 points per dollar using the CSP at Marriott.com.