I actually liked the interaction here, as it shows that Booster is really quite smart - on the verge of going OOC (if he hasn't already, but that seems to be the point...). As for the toast, I think the smiles there aren't lighthearted inasmuch as sad ones - it just didn't translate well. Wouldn't we all want to change something in the past...but then, how would that change the present in ways we never thought of?
I remember an old sci-fi story, where the problem is: even if you changed the past, all you would do is create a divergent timeline. your past would still be the same...