Twin/full/bunk beds etc?!

My husband and I hope to have a big family (at least 5 kids); we have 2 right now (3 & 1). the 3 year old is moving out of a crib and into some sort of bed. Trying to decide if it makes sense to get a full size bed (more fun for reading books before bed as a fam) or a twin? we have the space for a full. but eventually the younger will likely move in the room with her older sister. then would it be better to just get bunk beds now? twins next to each other? share the full? its a big room but I don’t think we would put two fulls in there (just kind of ridiculous, right?!). Thanks for any thoughts!!