Two and a half is a tough age for high lake fishing. They are getting to be too big to carry and they can’t walk very far yet. So you have to look for something that is a drive to or short walk. Drive to lakes like Leech and Dog on White Pass are good bets. There are a lot of interesting drive to lakes down by Mt Adams. For short walks try something like Kelcema off the Mountain Loop Highway. Or Lodge on Snoqualmie Pass. Mirror Lake, east of Snoquamie Pass is a reasonably short hike.