As others have said, I think Dawes asention to the presidency probably makes the Great Depression shallower, but imho it'd still be one of the worst ressessions the US (and the world) have experienced to that date.
Though Dawes may want to regulate the Stockmarket, would the congress go along with that? Normalcy was more popular than ever in 1925, which could hinder Dawes attempts to prevent any kind of depression occuring, along with any internationalist ideas he may have.
I still think Dawes beats Smith handily in the 28 election (though probably not by as healthy a margin as Hoover did in OTL).
I think Dawes reacts differently to Hoover after the economy slumps though, that'll be where he could make the most difference I think.
In 1932, I can see FDR as the democratic nominee still. He's their best bet in that year and since Dawes has prevented the worst of the Great Depression, the republicans won't be in as much dire straights as they were in real life.
That said, the Democrats are still favoured to win and although the victory is somewhat closer, FDR beats someone else (Dawes probably wouldn't go for a third term imho).
I'd say you're in to guess work from that point on-does Hitler come to power? If so, are the countries he invaded in OTL better able to defend themselves, because of the improved economy?
Without Hitler and World War II, FDR chooses not to run in 1940, stepping down at the end of 2 fairly successful terms as president. You may well see Herbert Hoover win in 1940 if that happens-he hasn't been in office during the worst depression in US History, so chances are he's still popular with the public at large.