My 2.6 year old finds changing activity very hard, as I'm sure is very common. I always prepare her for what is happening next etc (I'm a special needs teacher so this is second nature anyway), but it's very difficult when she's involved in play to move her on. She is always engaged in imaginative games (has a whole host of imaginary friends) and these would go on forever, regardless of the need for bedtime or anything else I need to do. She will argue the hind leg off a donkey and always has a good reason (in her opinion!) for carrying on with her game. It's hard for me to reason with her imaginary friends! I'd rather avoid the distress and tantrums of just doing the next thing anyway (such as taking her upstairs to bed regardless).
Any tips, if you can make sense of that waffly post!