My 3-year-old son is doing really well with potty training at home (3 weeks now) - I've been really fortunate; however, he won't use the toilet/potty when we are out which results in him wetting himself multiple times. We're travelling to my parents tomorrow which will take about 2 1/2 hours door to door. Should I put him in a nappy just this once or put him in his trainer pants? You know what trains are like - there aren't always toilets in each carriage and they're horrid anyway. I'm panicking!