both of you decided to try for 2nd kid is mainly becoz of other pple's pressure or you merely wanted your daughter to have a companion or a mixture of both?
if the reason is for your daughter, then slowly let nature take its course. Personally i m also faced with lots of comments from pple asking me to try for no2. I have "model answers" to answer them oredi lOlzz.......
Age wise i agree that expecting in late thirties might be draining on energy and health, but its still possible to have a healthy baby. I have seen some colleagues who were preggie at early forties even. Sorry to hear about your m/c *hUgs*, like what you r doing now, to take care of your health and body for the next pregnancy, i think its perfectly alright.
For the time being if both of you have made up your minds to have no2, i think you should not worry about too many things at the moment coz you r adding on stress unknowingly.
sometimes things might change if you have no 2, so if both of you have set up your mind, just think ahead and await the good news.