I wouldnt, not when the toddler is nearly 3. Defn a good carrier, and if your really worried, you can get a side by side on ebay for well under $100.
My DD#3 is nearly 3.5....and most times we are at the shops she prefers to walk...sure there are times where she wants to sit down, and lucky i do have my side by side stroller, but more often than not i end up push the twin stroller with only 1 kid in it !!!