I am due on Thursday and I have a 14 month old (15 months on the 16th). We planned our boys this close together as we figured we are already in the chaos and once we are through the wild sleepless and toddler stages then it's done as we only wanted two alongside our 14 year old. I can't give you coping advice yet as I haven't had to go through the madness myself yet but I things that have helped me cope with pregnancy with a mad climbing and energetic toddler was the following:
Make a safe space for baby to crawl and walk in. Our ds started walking spot on 12 months and we have invested in magnet cupboard locks. They are an absolute God send. You can attach them now and keep them unlocked until baby starts exploring. Both when you are heavily pregnant and have a new baby the last thing you need is to get anxious from having to chase you eldest around like mad!
Wash and organise new babies bedding and clothes now whilst you are still in the early stages of pregnancy and put them into a cupboard ready. Now I am the size of a space hopper I have no energy with looking after my toddler so very glad it's just one thing sorted.
We upgraded our travel cot to a play pen for ds so he would get used to being in it for short bursts by the time baby comes (and so I can pee and cook and know he is safe). This will allow you to keep the babies apart if you need to nip to the loo or deal with any nappy crisis!
I know I have latch problems so this time I have been stock piling colostrum syringes ever time I go to the hospital. From 37 weeks I have been expressing every day to build a stockpile in advance just incase (if you plan on nursing and feel it might help you ofc).
I think the research I have done is to become as organised as you possibly can in order to survive the first few months:
Make up your toddlers lunches in advance, cutting fruit and veg in bulk.
Try to lower your housekeeping standards.
Organise chores with hubby, one keeps kids entertained whilst one cooks etc.
Consider getting todder their own baby doll if they are overly interested in baby so they can feel involved (our children are too small to explain in depth what is going on) but they still want to do "monkey see, monkey do".
I wish you so much luck and joy mummy bear, it will be a bit mad but everyone assures me it's going to be worth it xxx