I would have said it didn't matter as long as they were all the same. Without seeing it, I can't really say. Use your judgement and decide if they're really that different. Taking out bind offs isn't that difficult, and there aren't that many, so if you don't think they'll be good enough, then you do have that option.
If they're close enough and you think you can fudge with a little seaming if necessary, then leave it. Like you said, it's a kid's sweater, and kids' aren't particular.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry