I find the suggestion of Rodney asking Ronon to go a bit less off-putting, only because it's more difficult for Ronon & Teyla to go to Earth - there's (presumably) paperwork and whatnot, plus Rodney knows Earth funeral customs best. So Rodney is the most logical one to accompany John back, and I could see the whole team assuming this. In that case I see it along the lines of Rodney mentioning, "I can't make it," and Ronon going, "Okay, me then," more than Rodney outright asking (Teyla's pretty much out at that point, because John turning up with an unmarried pregnant woman as his escort would invite way more questions than he'd care to field...)

(I admit I'm biased, though; much as I love the team, there's a part of me that wants John & Rodney's friendship to be special, that wants Rodney to be John's first choice for such brotherly duties...I'm a bad team-fan! *feels guilty*)