I found DS coped well with the change, however I must admit I have let him watch ALOT more TV since DD arrived. When DD was a newborn for the first 2-3 weeks it was easier, once she woke up a bit and started madly feeding from 4-8pm most evenings we struggled for a couple of months.

From a Mummy perspective - I've found that my own time has simply disappeared, having 20 mins to myself to sit down with a coffee and jump on the computer is a sheer luxury these days. I tend to do everything else (online banking, FB, emails etc) on the iphone while BF.
Get dinner sorted as early in the day as possible
Always have a snack/drink available for the toddler before you start breastfeeding (even if they say they dont want one)
Get the toddler to help you as much as possible
Try not to fob the toddler off when they need you, I found that DD was most happy to lay on the floor with us while we play and everyone is happy this way.
Once the baby is big enough and assuming you have one, sit them in the reclined high chair to join the family at meal time. We found DS would fuss and not eat his dinner if I was BF on the couch, so once able, we returned to family dinners at the table to restore some evening sanity.
Oh evenings, try to be as organised as possible, I find this the most challenging time of the day - dinner, bath, bed, constantly feeding baby in the early days. I bath the baby and toddler together (teach the toddler not to splash while the baby is in the bath)
Be prepared that your partner will feel very neglected. We are struggling a bit with this at the moment. Two kids takes up most of my waking hours and as soon as they are in bed I just want to go to bed, but I know DH wants to spend time with me too. So we are trying to have an 'at home' date once a week, eg movie night with nibbles etc where I am totally spending time with him (phones, computers off etc)
My GF threw me a mothers blessing before Bubs #2 arrived and filled my freezer with cooked meals (I bought an extra chest freezer for the garage). I still have some in there months later, a total life saver many times over.
Also, I shop online (Groceries from coles online) and have a cleaner once a fortnight to give my house a big clean (bathrooms, floors, all the dusting etc), and one of the first things I do each morning is put a load of washing on.

Sounds hard, but its totally worth it, just try to be organised where possible. If only I could get them to have a daily nap at the same time, I'd be totally on top of everything, however, this has happened twice since DD was born

Having two is lovely, the sibling love is divine, and having a house full of baby/toddler laughter is the best thing ever