Is your partner available to help out with the cosleeping? We usually transition toddler to dad doing bed time and co sleeping about 6 weeks before the new baby comes.
If not, then I have also done plenty of nights stuck in between a newbie and a toddler. That can take a bit of work to get everyone in the right position, but I’ve always found my toddlers (ages would have been 2.5, 3 and 2.5) happy to cuddle up to my back while I feed the newborn in the night.
You will sleep again, I promise. (I mean, I have no actual evidence that this is true, I haven’t slept all night in 9 years
but it has to be true. It has to be……!)