Singulair Paediatric- 4mg

My little was diagnosed with asthma 12 months ago, he's 3 yrs old and suffers really badly with it. Yesterday i had to take him to an out of hours surgery and Dr there prescribed him Singulair Paediatric 4mg. The Dr told me to give him the tablet every night before bed, it has to be sucked or chewed. The problem is, its obviously not a nice tasting tablet and i'm struggling to get him to take it. I was just wondering if anyone knows of an easier way to get him to take it?? Am i allowed to crush it up and give it him with a spoon of yogurt or anything?? I'd reaaly appreciate any advice anyone might have to offer...... Thanks. xx