am in a similar position as you, but i don't think i want my 3rd child because
1) my #1 is 28mths and #2 6mths, 2 girls, 2 years apart is alot to handle....
2) ideally i would wait till #2 is at least 2 before trying for #3, but even if all goes successfully, i'd be 38 when i had #3, i think it would be hard for me physically to take care of three at that age. i'm a very hands on mom, and 2 girls is already alot of work.
3) if #3 is a girl, it'd in fact be "easy" except for the education fees, because everything (well almost everything) would be hand me downs - with a boy, you'd buy everything new.
i have 2 healthy girls - i think for me personally, i will stop, if i could guarantee a boy for #3 of course I'd have #3 (my husband is the only boy in his generation - the family surname stops with us! ) ha-ha, luckily for my in-laws it doesn't seem to be such a big deal. having 2 girls is good too they can communicate and share many things as they grow up, girlie things etc. my hubby has my sisters 2 boys to play with - he gets his "boys" time. of course he'd like a boy, but he is already feeling the pressure of paying school fees, and our daughter is only going to playgroups! why not spend more time and money on your existing two? having 3 really close together is good for the kids in the long run, but in the meantime you will have a very rowdy household! (my sis has a 5yr old, 4 yr old and 2 yr old)....just for you to think about...