I have a 6 month old and 2,5 yr old. I found songs, books, role-play toys, pretend teapot n tea cups, visits to mates with kids the same age and letting the toddlers play, singing at the library, visits to granny's, pee-bo using a book/piece of paper are all good... and lots of cuddles, lots when baby's asleep, but also with baby at boob and toddler on the other knee - it is possible!
Also, colouring, playdough and if all else fails, as lifeas3plus one says... cbeebies, and getting the kids classics out - jungle book, dumbo, mary poppins, the gruffalo etc, which are just about right when you're knackered!
Believe me, you will become the queen of multi-tasking, and playing with your toddler whilst feeding the new bub will soon become second nature!