I'm not sure the FA Cup kids makes much difference. Had they won, they might have had more confidence and momentum. But on the other hand, yesterday will have hurt them. "Remember what losing at Wembley felt like and don't repeat it" will be their motivation. They'll throw everything at it.
Even if they lose to Leicester again and need to win on the last day of the season to qualify for the CL, I'm not sure it will harm them. Yes, they'll have had to play their best side. But then again, they'll have been playing together, whereas we'll have been rotating, and we may not be quite in the groove.
From our point of view, there's no doubt that if we play as well as we can, we'll win. But the fact that we've won the league and can focus on the CL final is also creating pressure for us. We are spending 3 weeks disguising on one march - I think that's less helpful than the "just think about the next match" approach.
Who knows, it'll be close each way.