I don't have daughters so this isn't an issue for me, but as always, I have an opinion!
Have times changed? I have photos of me as a toddler upwards, in bikinis, and I don't look at them and think it's inappropriate. Occasionally, if my swimming cossie was wet, or it was an impromptu stop, I'd be paddling in just my knickers. Is that more or less inappropriate than a bikini? Is a bikini top, given that it covers the nipples, the inappropriate part?
My mother would be horrified if she thought her choice of swimwear was sexualising me.