Try going out just you, her and the kids in some sight seeing areas like lake Bogoria so out of town. Build the family unit first by making her know by you all being out of the home setup you enjoy the family unit. Do this repeatedly as much as you can afford.
When she becomes comfortable with this holiday like family outings, introduce slowly getting to those bigger family get togethers, weddings, birthdays etc but remember the word
slowly lest she pull back on all the positive impact you have made.
If she cann't stay longer in this groupings, granted allow her to leave mid way. Whenever she does this make apoint of telling her how you appreciated her company through what she likes and hopefully you shall have a different person all together and both will enjoy each others activities.
The problem with the world is that the intelligent people are full of doubts while the stupid ones are full of confidence