Definitely education and all things related to education. I come from a three sibling household and I've seen how much my parents spend to send us all to university. My elder brother went through the non traditional route and worked full time while he did his degree part time. My younger brother went to a private uni so my mom took out an education loan and he is nearly done paying for it after 3 years post graduation. And I went to NTU and my dad used his CPF to pay for mine. After graduation, I had to pay in installments by cash money to my dad's CPF ACCOUNT. Reckon my parents won't be able to pay for all 3 of us otherwise.
You would absolutely have to consider your financials - probably the largest part you would have to consider. how about when they get older? education costs? your monthly spend - can you afford it? maybe it's best for you and your hub to sit down and really go through your expenses :)