Christmas guests: heat factor in BA

My entire family is going to come to visit us over the Christmas holidays, mostly from New York City and Seattle. Are they going to be uncomfortable in the heat and humidity? They'll be here from just before Christmas until the first week of January unless I tell them to stay put. Thanks!
Thanks for the insight. This is sounding like a bad idea. I want my family to come but I also would like them to be speaking to me at the end of the day. "Hey everyone, pay a fortune in airline tickets to come down to BA and sweat." I was thinking maybe of trying to rent some houses in Uruguay on the beach as a plan B. Any experience with that?