Nope.
*DO---N!*
They have to at some point, facing Big Mom crew is not really a part of their mission, and the said mission is to take away Caesar & Momo far from Dressrosa, far from Doffy and others for the sake of their alliance. If Sanji can't even ensure that in whatever way out there, letting his emotion or pride fighting BM crew till the end to lead his action, then Nami and the rest won't be safe plus they might even lose those two cards of theirs.
I assume Sanji's words to counterfire BM crew is still stand, until it's proven otherwise in upcoming chapter. Hopefully it shall never be off-paneled again.
I've been wondering what else people want Sanji to end up being? If Sanji's group get caught by BM, you'll thrash the guy for being weak, and if Sanji's group manage to escape, you'll criticise him as well over the reason of cowardice. If Sanji ever put up a fight, you'll say he's not strong enough to defeat the crew so they better run while they can. That's quite a prejudice.
Is that island Zou?
I haven't seen anyone discuss the island.
People mentioned it, but not as often as Kaido. I still have my doubt, but it does seems like Zou. Idk if the island is named after an elephant or its traits, or has other meanings, but if the elephant that the sheep guy rides on is included as a hint, then it is truly Zou island.
Multiple is not an option

It only can be used once in certain interval, and they already did that when Law was facing Doffy to get them outta Green Bit area. Franky's not there to refill the cola, and nothing we see so far shows that anyone in Sanji's group goes down and do that. Coup de Burst takes a bit seconds of time to be launched, now we're talking about Yonko's crew here, no way in hell they would give them such spare time.
Still unsure how it had actually turned out, but if they managed to escape because of CdB, alright then. Not gonna change there must be something happened before that one.