We were there a couple of weeks ago with our DD who is 4 and it rained one day while we were there. Because of the bad weather, they had some activities set up in the community hall that were geared towards families. Check your daily IWA or ask the front desk and they can let you know what activities are planned for the day. I would recommend the spa, but the only downside is that, depending on how hard it's raining, you might miss out on the lovely garden and other outdoor activities there. Aulani is a lovely resort and you and your family will have a wonderful time!