It depends on your pregnancy and your health. Some mothers are able to continue breastfeeding throughout their pregnancy whereas some have to stop due to certain complications. You can try to continue feeing and importantly ask your gynae, if its ok. Secondly, assign breast to each child so they don't share & there will always be milk for them.
i latched my toddler till i was 5mo preg when my milk dries up. He had occasionally latching till i deliver. but the moment i deliver, he refused to latch on already!
if you want to tandem feed. assign boobs to ur kids it's also to prevent them from sharing and spreading germs if one of them happens to be sick