If your oldest will be four or older by the time your 2nd baby arrives, you may not even need (or want) a double stroller — or you may only need it on occasion. Outside of the weight capacity problem (usually 40-45 lbs per seat), most 4-year-olds are too big (height-wise) for many of these stroller seats.

Most 4-year-olds can still comfortably fit in a double stroller, but it depends heavily on the child's height and the specific model of the stroller. Most high-quality double strollers (like those from Baby Jogger or Bob) are rated to hold up to 45 or 50 lbs per seat, and the average 4-year-old weighs between 34 and 40 lbs. The main issue is usually "legroom" rather than weight; taller children might find their knees hitting the front frame or their heads touching the canopy. In a theme park setting like Disney World, using a double stroller for a 4-year-old and a younger sibling is a highly recommended strategy, as the "miles of walking" can be exhausting for small legs. If you are renting a stroller at a park, the molded plastic "double" versions are specifically designed to handle older children up to 100 lbs combined. While a 4-year-old might walk perfectly well at home, the intense environment of a vacation often makes a stroller a vital tool for preventing meltdowns, providing a mobile napping spot, and helping parents maintain a faster pace through crowded areas.