Trying to attend a DR destination wedding on a budget, looking for alternatives

My Fiancé and I have been invited to his sister's wedding in late January 2017 at the Grand Palladium Punta Cana Dominican Republic. We can't afford the $2000 per person price tag though. She is going through SunWing with packages for 1 week all inclusive. There doesn't seem to be an option available for a 3 or 4 day option to price compare.

Does anyone have any advice to offer for alternatives? I've been searching for nearby resorts and places that aren't all inclusive and shorter stays but it seems the deals are all last minute, but I don't think it's right to not be certain we can attend her wedding until last minute.

We will be travelling from Toronto. Is it best to talk with a travel agent, or would it be cheaper to book our flights and explore AirBnB or cheap hotels?

ANY tips would be so appreciated! I haven't been on a vacation that wasn't a road trip before, so I'm way out of my element. Thanks.