Wedding for 150, rough ideas please :)

pulled pork 90lbs raw pork
pulled chicken I'd do legs and thigh (not quarters) about 120pc

party potatoes 35-40lbs
baked beans 2.5 full size pans with 2 10# cans doctored up could do 3 but will probably have leftovers
cole slaw 4.5-5 gallons

As for cost your pricing could be different than mine, plus you make have to buy some thing that won't all be used at this event so that will drive your costs as well. For me I'd be around $3.25 per person cost (without figuring it up)with buns and sauce. So you will likely be say $500. I'd make a list of your needed supplies and price it all. If it's close to my figures I'd tell them to budget $1000 that way you have coverage for wood, charcoal, foils, gas, ice, plates, sterno, etc which were not in my figures I only had the food cost in there. I'd be at about $15.00 per person to cater this meal.