I do not know to deal with kids...Help!?

The other day I took my 3 year old cousin to chuky cheese and he asked for an icecream.Unfortunately the icecream machine was broken and I could not get him one.He threw a big fit and started to wail like crazy.I was totally freaked out and did not know what to do.I got angry ,I tried to explain,I tried being soft,I told I will take him home but nothing worked.People were staring at me and it was so embarrassing.I am not a mom yet but this incident made me upset.How do you deal with kids like these?