The Friday night function is themed "Bollywood" so wear your finest and loudest Indian outfits. The Saturday function is either English or Indian attire. Semi-formal would be the best way to describe the requirements, but remember it's Fiji and it's hot so have some fun.
Of course you can bring your children, however we won't be able to accommodate them at the formal functions for a number of reasons. One of the great things about Fiji is the quality of child care services. Here is the link to the babysitting and childcare services at the Sofitel. Most hotels have similar services at their sites also. https://www.sofitel-fiji.com/clubs-and-lounges/niu-beach-club-for-kids/
Yes
No.
It's Fiji - so hot and humid. March sits in the Fiji summer season meaning a truly tropical experience. The maximum average temperature reaches 31°C / 89°F and the minimum average temperature is 23°C / 73°F usually at night. Fingers crossed it does not rain!