It depends on your DD. At ages 2, 3 and 4, mine wore Princess dresses from open to close in the parks. (at age 2, she insisted on it every single day of the trip too- she refused all regular clothes). They get a lot of attention from CMs and guests who call them Princess and compliment their dresses, and once my DD got a taste of that, she wasn't taking the dress off. By age 5, only wanted to wear a Princess dress all day on BBB and CRT day, but that day, she still wore that dress from open to close that day. Other than that day, even if we went to Akershus, she usually just wanted to wear a regular dress, not a Princess dress. That lasted through age 7. At age 8, she was pretty much over Princess dresses even though she still liked the Princesses- she wanted to wear her Anna Dress to meet Anna and Elsa at DL and then to have a Princess meal after that, but when we went to WDW later in the year she didn't even want to wear her Anna dress to meet A&E- she wore a Frozen T-shirt that day instead.
If your DD wants to wear her Princess dress all day in the parks let her. My DD never had any trouble going on rides or anything else with the dresses. I agree with the sensible shoes though. Princess shoes are not good for walking at WDW! You will see lots of little Princesses with tennis shoes underneath!