It sounds like there's a couple of concerns for you here. Feeding a toddler and then feeding to sleep. From my experience it is possible to stop the feeding to sleep without stopping feeding my child completely.

With DD1 around the same sort of age, i asked DH to come home early & help with bedtime every night for a week as follows: i breastfed DD1 around 30 mins before going down to sleep then she would have a drink of water and then go into the bedroom with DH. He would cuddle her or sit in the rocking chair and stay with her and comfort her until she went to sleep. There was resistance of course for a few days but by the end of the week she was happy to be put down to bed by DH and then i was able to settle her in the same way and eventually to us popping her into bed, twinkle twinkle song and closing the door to her snores! BTW we made sure she wasn't teething or ill or anything before we started.

This helped to stop the 'feeding to sleep' pattern for us. There is also a lot of great advice in the No Cry Sleep Solution book by Elizabeth Pantley which is also popular. I went on to feed her till she was 2.5 yrs and then she stopped.

Oh, and it's quite possible to expand the family whilst breastfeeding - i've had 2 more babies since!! To be honest DTD doesn't take that long any more........!!

good luck