I think you will all be fine. Singapore should be safe unless you really get off the beaten track where I think avoiding things from street vendors might help put your mind at rest, ice-creams (dairy products might not have been stored well), having bottled water where possible and availing yourself of packaged goods from the supermarkets for snacks should be fine. Wash fruit or opt for fruit that you have to peel (eg bananas) might be better than sugary snacks from home that will only fill up your luggage. Maybe ask GP before you leave about medicine you might be allowed to bring, just in case.

Check the rules for Singapore there will be plenty of travel advice on official travel sites. The food in Singapore is tasty and we have found it safe.