Hi, Elle, and welcome to the forum! It's nice to see another Austinite around! I just moved to England from Austin in November.
I do hope you are aware of the financial requirements which must be met by your husband in order to be eligible for a spouse visa in the UK. Also, I believe your husband needs to have a job offer prior to applying for the visa, with a start date of within 3 months of arrival to the UK. Or, he can move to the UK first, secure a job which meets the financial requirements (and hold it for 6 months), and then the rest of your family can follow. I'm not sure what the exact figures are, as I did not have any dependents when I applied, but this information is all on UKBA's website, which I'm sure you've seen! (:
One thing upon which I can comment with confidence is the flight info. Generally speaking, I found that round trip tickets are cheaper than one-way. However, when I came over to England, I had purchased my one-way ticket from a site called Oojo - it was nearly half the price of one-way tickets from the airlines themselves. Also, I have heard of a site called SkyAuction, though do not have personal experience with it. They offer one-way Virgin Atlantic flights from a few US cities. You bid on them, and may purchase up to 8 flights for the winning bid. Sometimes they are as low as $100.
Hope that helps a little, and best of luck to you during your visa process!