I just use black and gold butter, never had a problem. Leave it out to go soft and often just zap it a bit also if need be. I use the recipe found in the WW birthday books for Vienna cream;

125g butter
1 1/2cups icing sugar
2T milk

have butter and milk at room temp, place butter in small bowl of electric mixer and beat until butter is as white as possible (I just beat til it is nice and whipped). Gradually add half sifted icing sugar, beating constantly, add milk gradually then the other half of icing sugar and beat in. For chocolate add 2T cocoa to the icing sugar. I've never had a problem, once I didn't read the instructions and added all the milk, butter & icing sugar together at the start and just started beating....turned out great.

Otherwise, my sister just did a cake for her DD and she used the tubs of Betty Crocker icing....they are yummo!!! she said it was easy to tint, saved her lots of time and problems...only thing it didn't smooth as much as the Vienna cream but all the same great and great tasting.

i have found a ripper cake for my DS2 first birthday and as it is all covered in smarties I will just be getting Betty Crocker to make my icing