So, they are both really expensive places...HOWEVER, they were both having huge sales the last time I checked...I love j.crew's "crewcuts" for little guys...they carry linen type pants, those darling plaid shorts that can look very beach formal w/a white long sleeved button down (you can find those shirts or similar on clearance at old navy)...I also love mini boden (a UK store, online).
I know they are both VERY expensive, but, if you can find a sale, it can be great!! I have found amazing prices at both places...I NEVER BUY FULL PRICED ITEMS for my children at either of these stores! Anyhow, I believe Dallas finally got an actual crewcuts store, so, it might do you well to pop into one...and head straight for the clearance rack (it's brand new though, so their clearance might not be that great, and it's in a wealthier shopping district, so, the demand for full price items may be higher)
ALSO, if all else fails, just pair a formal button down + tie w/some less formal (but cute) shorts and some flip flops or white tennies...OR put your little guys in some easter pants (target always has seersucker around easter) and a white solid polo + stylish flip flops (old navy or gap).
haha, i just read this and realized I sound like a shopaholic! lol...i really don't spend tons on my kids...I actually shop all sales!