My personal feeling is that it is more important to have pre-existing conditions coverage than to go with any particular company. That said, if you or a traveling companion is a veteran, or active or reserve military,
http://www.usaa.com/ usually has very good deals on travel insurance, and insures children free, which is a nice bonus. I'd recommend either their TravelInsured Worldwide Trip Protector, or Worldwide Trip Protector Gold.
If you are sure your insurance will not cover you outside the country, or if it would be a hardship to wait for a check, you might want to make sure your insurer is primary and not secondary--there is an extra charge for that with Worldwide Trip Protector, and Worldwide Trip Protector Gold, but I would still see if the overall charges are more or less than others. Another poster had good luck with a medical claim with TravelInsured, so that is an advantage.
To get pre-existing conditions coverage, you generally have to buy insurance within 14-30 days of your first payment. The one major exception to this rule is CSA, which you have to purchase within 24 hours of your final payment. If nobody in your family has been ill for several months, and has had no checkups or changes in their medications for several months, it may not be absolutely necessary, but I would worry without a PEC waiver.
Remember, if you need to cancel a trip due to a family member's illness, the pre-existing condition clause may come up.
If you want to compare several policies,
http://www.tripinsurancestore.com/ does an excellent job of comparing the advantages and drawbacks of a number of policies.
http://www.insuremytrip.com and
http://www.squaremouth.com/ are also good.
Whatever you decide, I hope you have a wonderful trip and never need to make a claim.