If you need a child seat for a rental car, reserve one ahead of time. Make sure the brand is of a quality level you respect, or consider taking your own along. All-suite hotels and motels offer plenty of space, with a room for mom and dad and a sofa bed in the living room area. Many have kitchenettes or provide breakfast and offer free parking. Renting a fully equipped condominium is also an option for families.
Camping is a great family activity.
Weekend rates are available at most chains, and many define the weekend as Thursday through Monday. At some places, you get a free third night with two weekend nights booked. All-inclusive resorts help you keep to your budget, with most food, services and activities included in the price. Pick a place with children's programs and babysitting for infants if you'll need it. Off-season, ski resorts can be a great bargain.