I would not try to have multiple families book at once. You will be able to charge a premium if you have a 5 bedroom house! Yes there will be a smaller audience but the price you can book for should even that out. Families will not generally feel safe sharing another space with strangers, especially if there are children. Try finding some other ways to make your place stand out. Maybe it’s especially great for kids and you have 2-3 of the rooms decked out in fun kid stuff, bunk beds, tents, climbing wall etc. or if the property has space for outdoor events you can advertise as a small venue for weddings, family reunions, etc.
learn about your market. Who comes to visit there? Who is your target audience? And then design and market your space with that in mind.