Transitioning to toddler bed

I have a 2 year old and I'm due in November with baby #4. They eventually will share a room once baby sleeps through the night. He will probably stay in our room the first year. My 2 year old is still in a crib. Should I try to switch him to a toddler bed before baby comes so that I'm not up with both kids at night or just wait a little longer? I also have a 10 and 8 year old that went to toddler beds at 18 months with no problem but they were very laid back toddlers and actually stayed in bed. My 2 year old is totally different and I feel like it's going to be a struggle.