I don't see anything particularly amiss in Wentworth's behaviour to Henrietta and Louisa.

As far as we know his intentions are honourable. In Ch7 we find the following passage:

It was now his object to marry. He was rich, and being turned on shore, fully intended to settle as soon as he could be properly tempted; actually looking round, ready to fall in love with all the speed which a clear head and quick taste could allow. He had a heart for either of the Miss Musgroves, if they could catch it; a heart, in short, for any pleasing young woman who came in his way, excepting Anne Elliot.

His disposition is confident, witty, talkative and outgoing. The people of Uppercross, young and old, respond with universal eager admiration, with warmth, friendliness and flattery. The Miss Musgroves and the Miss Hayters have scarcely clapped eyes on him before they declare themselves "in love" with him,(or are in "a little fever of admiration"). I think the young ladies' unguarded behaviour is quite as deserving of censure as the Captain's. It would seem churlish if he did not respond to so much attention from them all. He does not appear to be singling one of the girls out at first. When Henrietta has made it up with Charles Hayter and withdrawn from the competition, then Louisa puts herslf forward to engage his attention. Perhaps she will succeed in catching his heart.