I think having D3 play on Saturday would be better as previously mentioned they are normally younger, but perhaps over the summer to make it fair have D3 play on Friday and let D2 play on Saturday, then when the summer ends go back to D3 on Saturday.
Just an idea, you could use this as a test year and if it works implement it in the long run but if it doesn't work out then stick with D3 on Saturday all season long.
Best of luck this year