When we get together with Possibility's family or other friends it's always potluck! They're welcome to come without a dish or drink, it just means there won't be as much to share but we certainly don't go out and buy extra stuff just in case, lol. We keep water, coffee & tea around but anything else, like soda, alcohol or special drinks friends have to bring themselves. They can also give us money ahead of time to supply what they are wanting to bring.
There's no reason for you to stop the get togethers entirely. Just make it clear that you can no longer foot the bill for the entire thing, others need to chip in in order to make them happen the way they have been.
Speaking of....I need to get in touch with Breathes & Possibility's wife & husband to check on the date for our next pot luck to make sure no one has any plans for that particular day, lol.
There are as many ways to do polyamory as there are people practicing it!