The divorce may be finalized. You are beginning your new life. However, you may still like your former in-laws and they may still have positive feelings towards you.
If you have a good relationship with your ex-spouse, it may be very easy to continue seeing and speaking with your former in-laws. It makes it even easier if you have children. Positive feelings involving everyone can make the children's transition easier.
It may be more difficult if you do not have a good relationship with your former spouse. It is still possible however to work to have a good relationship with the in-laws, if you are willing to meet people halfway and understand boundaries.
You are no longer married to your former in-laws' child, so there will be a transition to the relationship. You must acknowledge this. In fact, you may need to give your former in-laws some time and space to accept the divorce. Therefore, it is important to not push if your former in-laws if they say they need time. Please respect their wishes. If you push them, you will drive them away and perhaps ruin the relationship in the future.
If you are invited to their home for an event with your child and their grandchild and you feel comfortable attending, feel free to do so. It is very important that you not condemn their child in their presence. This would include making negative statements to other party guests. Also, do not talk about the details of the divorce or how hard it has been.
Focus on the positive. Rebuilding your life will also mean you will be forming new relationships and accepting changes in some other relationships.
Just remember that the people you involve in your life should also be respectful to you. You should not accept people being rude to you. If your former in-laws are not positive or try to blame you for the divorce, do not accept this behavior. Step back and give them some time and space. Perhaps their feelings will change. On the other hand, you may have to accept that a good relationship is unrealistic.
It is important to be patient and let relationships evolve. Remember to be respectful of other people and their feelings. Expect the same of them and hopefully you will be able to enjoy a good relationship with your former in-laws.