If in laws want you to attend a celebration hundreds of miles from where you live(ieeveryone travels to this different location to stay)
that one
it should not be made"compulsory"to attend
it would have been polite andpractical to discuss in advance of makingany accommodation bookings to check if you are likely to beableto/want to attend
that if you do not want togo your opinion should be respected and that people should realise that not everyone is likely to have the same idea of what constitutes a "fun" gathering.If such a gathering was relatively convenient, did not involve costly and involved travel and accommodation bookings, that then maybe some one might attend even if they did not reallly weant to, but under the circumstances, you cannot expect everyone to turn up.