I have been working part time in a job 3 days a week which I generally enjoy. I have 2 young children and it has been really flexible. My manager is leaving and I have been offered her job. It means an increase in hours to 4 or 5 days a week and there will be a certain amount of travel involved but a good increase in salary too. My DH is very keen for me to take it as the extra money would make a big difference to us. I am prepared to do it but I said to DH that he would need to step up as currently I do all the drop offs and pick ups at childcare, the cleaning, cooking, getting up in the night and sick days. I said DH needed to think about the job as well because it would have a big impact on his life too. His response was "we'll just rely on my mum".
MIL is ok (we are very different) and it would be fine to have her help out - she'd probably want to take the children for one day a week - and help out when we are stuck but I think that DH needs to step up too. He works for himself so could help with pick ups and drop offs if he organised himself.