1. Bait and Switch
This is a well used ploy for Chol Hamoed trips. If your family choose a difficult Chol Hamoed trip or trip that does not interest you at all, then just agree to go along with it. Then en route, ensure that you get hopelessly lost and land up at a more favorable destination to you. For example, if the family chooses to go to an amusement park then just somehow land up at a nearby bowling alley and say "well this must be where Hashem wants us to go".
2. Bemusement Parks
There is nothing amusing about amusement parks ever and even less so on Chol Hamoed. Avoid, amusement parks at all costs, promise whatever it is you have to promise and take the family out for a steak dinner but avoid bemusement parks. Even if the weather is great and the park is empty, amusement parks will feel hot and crowded. There will be no sukkah and at the end of the day, you will feel like it was an abusement park.
3. 'I Have Something Urgent To Do And Will Join Soon'
So the bait and switch is not an option and there is no real way out of a Chol Hamoed trip you really don't want to go on. Use the 'I have something urgent to do and will join soon' line. A variation of this is, 'I think we need to take a second car with just me in it'.
4. Better than bringing a friend
This is a great option for when kids want to bring friends on Chol Hamoed trips. You can suggest that it seems that the friend's family are better planners and suggest, why don't you just join your friend's family?
5. Stay in Shul for Very Long
Many of the toughest trips require you to leave very early, if you stay in shul for very long you may deem the trip no longer worthwhile.