Well the best solucion is to cross shoulder straps and buckle it like that because soon they will learn how to take them of if you don´t do these: The straps have to be criss crossed on there chest  Hope these helps

I agree, shoulder straps are WAY too long (even for my 15 month old). I'll try crossing the straps as someone recommends. I wrote to bugaboo letting them know the straps need a Redesign. Designing the straps for a three year old is ridiculous, at two and a half most kids start refusing a stroller all together.

This has been a common problem with the bugaboo. 6 months is usually the best starting age for the seat. There is only so much strap which also needs to hold a 3-4 year old. When the baby is young there does not need to be as much restriction on the strap compared to the infant car seat. Just keep a watchful eye or bundle them up to make them look bulkier as to not slip out of the stroller and don't go down really steep hills with the seat fully upright. Give it a little tilt to "bucket" the baby better.