breastfeeding is easier, imo in these circumstances. you can just pop babe on the boob, not faff around with formula, making bottles, heating etc etc etc. no washing bottles, sterilising, therefore more time for baby and toddler.
things i did (my dd1 was 24 mths)
bought dd a doll with a bottle to feed her doll with (although she fed her doll with her boob!)
when i went to feed dd2 i got dd1 to get her doll and we sat and fed our babies together (she would get fed up and go and do other things after about 5 seconds)
got dd1 juice, a biscuit or raisins or something and sat her on the other knee/beside me
let her watch her favourite programme on cbeebies or read her favourite book
phoned gran or daddy at the same time and let dd1 speak to them
em, dont worry, not all toddlers get jealous. sometimes they dont understand what happening, and all they need is a bit of gentle simple explanation.
there are books you can get to help you explain everything
best of luck with your little ones