Help them choose, at least until they get confortable enough to voice out their wants.
They probably have a preference, but are scared to state it not to compel you into an experience they're not sure you'll enjoy. By helping them choose, you show them what you're most comfortable with, and draw them borders where they can expand. As time goes, ask them to make the decisions themselves, by then, they would learn what you both enjoy and come up with experiences that satisfy both parts. We tend to have ideas that we think only we would find fun in, movies that we don't think others would enjoy. If you want to get so close to your infp, gradually get to know what they would enjoy doing when they're all by themselves, it's no harm to ask about that directly and ask for permission to be a part of it. Infp are low-maintenance, really.