It can get cool in October. We rode out hurricane Stan last year and with all the rain, the storms, and wind, it was cool...Not cold...but I am from Michigan...it is not cold till there is snow!
I take the same clothes no matter when we go although I am more likely to take a light jacket this time of year. If you are going out and about I would also take a rain poncho or small umbrella.
As to having dinner with the foster families... We always do this. We have three foster families involved! Usually they are tickled pink to eat at the hotel. We stay at the Marriott, and they have private rooms off of the dining room and that is where we eat. Usually, we invite them for dinner either the afternoon before they pick the boys up or have them for lunch the day they pick them up. I ask them off to the side because I would rather everyone not know that I invited them.
We always pay for a cab for them or parking if they have a car available. K's foster family does not have a car and it is a 1 1/2 hour trip by bus so I will give them money upfront to get to the marriott... At the hotel, if you do put them in a cab, you can always pay the driver up front.
We really enjoy spending time with the foster families and it seems that this is how we get to know them best. It is also nice to see how they interact with your child and how you interact with your child.
HTH,