3rd child?

Ok so I have too beautiful children. Boy born 2008 and girl 2012. I'm very happy blessed to have one of each  however my little girl is now dressing herself and becoming an independent little lady. I'm feeling very broody again(this happend with my boy too).....would it be mental to try for another?? When me and my DH were younger always said we wanted 3(been together 16 yrs since I was 16)I can't help thinking should this be it now.we are very happy even number family lol.we both work me part time I would probably have to give up work for a few years this time.what do you guys think am I being greedy ???