I was looking at a few places online but they seemed pricey. I don't know if it's worth paying more of if they're not any better than what I'd get at a big box store.
What experiences with swimsuits have you had?
It doesn't matter a lot where you get them, but my biggest piece of advice is to get a sun protective swimsuit with a decent amount of coverage - ie, at least the same amount of coverage as shorts and a t shirt. This is for both boys and girls. Yes, you still have to put on some sunscreen, but you need to use a lot less, and at least some of their sun protection will never wash off in the water. My 2 year old DD has a sun protective suit with a turtleneck style neck, long sleeves, and long legs. The size is actually a bit small for her (I bought it last summer and it was too big), so the legs are more like capri length, but it still provides an awful lot of coverage. She wore similar suits her other two summers as well. I've gotten all of her suits from www.coolibar.com. They're pricey, but I can't find anything else I like in her size at stores or other websites. It's tougher to find sun protective suits for girls. More companies are coming out with tankinis that include "rash guard" shirts, but they still have the traditional swimsuit bottom. That doesn't satisfy me.
My 8 year old DS this year has normal swim trunks and a long sleeved rash guard from Land's End. I could have gotten as good a combination for him from a big box store probably, but he really liked the style, and they had a sale going on. It's possible, though more difficult, to find long sleeved boys swim shirts at big box stores. This isn't a deal breaker with me at his age, but the long sleeves are nice.
I also want to interject that I highly recommend sun protective swimwear for adults as well. DH and I each have sun protective swim shirts from Coolibar. He pairs his with his swim trunks, and I wear mine over my suit.
Of course, on the small chance you'll only be swimming inside, none of this applies :). I still, however, want to stay that I find bikinis on little girls to be tasteless. For indoor swimming, I like to go with a one piece suit in whatever pattern my DD likes. She currently has a green Tinkerbell themed suit for indoor swimming.
I like Land's End for both kids. Good quality and nice sales. We all wear full length swim shirts in the water and beach/play. DS wears shorts. DD wears either a little swim skirt or a regular bathing suit on top of the swim shirt. The bathing suit on top of the swim shirt was her own solution to wanting a range of unsuitable bathing suits.
I LOVE the sleeves for sun protection. It really cuts down on sunscreen use/time/aggravation/burns. We have hoodie towels for the beach to change into if needed.