Re: Bike, Trike, Skuut for 21 month old?
We have a strider and DD has been using it since 18 months. I researched for the shortest seat height before buying it. We also have a hand-me-down Skuut and on the lowest seat setting, DD still can't use it (she's now almost 26 months). We often have the Strider in the house and DD goes down the hall with it. Outside she walks with it and has recently started cruising by lifting up her feet or running more with it.
It took a bit for her to get the hang of it to move along faster, but we only do it in good weather on weekends. Our friends with kids who practice more often have picked it up quicker.