Every individual is so different, so is their sex drive after kids. Especially women who generally have emotions rule their sexual experience. Is there really a fail-proof way to have a genuine desire to hit the sack?

No fool proof way like there is no fool proof way to make sure u will agree to a salesman pitch. Rekindle the romance is a good idea. Best if she is given the chance to relax and kids are away or u two have some couple time. However, do not do it w a hidden agenda. Enjoy the 2-persons-world. Also if u want to have sec or feel that sex needs to be increase because there is practically none then u also need to talk about it too. Slow n steady wins the race ya