Hi, TripAdvisor is primarily a site to help travellers help themselves. We don't know you so the best person to make the decision on what to see and do is you. To make the most of your trip, you are encouraged to do some research on your own as must-sees and must-dos vary according to one's interests, demographics, energy level and budget.
A guide on activities for children written by our DE Avanti_SG
Singapore is full of activities, have a look at the following links to see what you like -
Once to have constructed your itinerary then feel free to post it on here if you need furthur help :)
Thanks all for sharing insights.