Family vacation

I am trying to plan my first family vacation, hope the plan can be materialized in this coming Christmas. I am so craving to have a good quality as well as relaxing vacation, but i have 3 little kids and the youngest is just about a few months old baby. Gosh, can anyone tell me how to start my vacation plan? It sends chills down my spine when i just about to think of the baggage, 2 adults plus 3 little kids, gosh, the baggage may definitely exceed the allowed weight. Budget is tight so i definitely have to well plan everything. As for the hotel room i wonder can all the 5 share a room? Be frankly, our family do not need any luxury hotel room, as long as there is beds and attached bathroom then it's enough for us. Having said so, i wonder does the hotel guy allows 5 of us squeezing in just a room?