fifi,
actually 1 year in advance is quite a good time to start hunting, esp yours is a Sat dinner. and good that your mom is NOT taking any tables, you have less worries... probably you can even earn $ from your banquet to cover costs for other stuff! usually people lose money because of the ang bows given to the brides' family. (but that technically shouldn't be considered as a loss but more like wedding expenditure)
This is what i did for my wedding: You must think of how much most of your guests (ur friends, FH friends, relatives) are going to pay for your Sat dinner. (this will of course depends on the 'type' of venue) if say u thinking of 5 star hotel, i guess on the average u will get, say $100 a guest? (or whatever the market rate it is for a normal 5 star hotel sat dinner)
Then look at the different 5 star hotels, ask ard for their prices, whichever that is ard $100 per person is the one you should probably go for, if the perks are not as good as the $130 hotels, don't worry, you can always bargain for more. Take taxes and also drinks (house wine, your own wine and corkage) into consideration if you have a large party. Also remember to include 1 table's worth of money into the loss because that's the bridal table.
If you don't mind losing a bit of money, you can set the max amount you willing to lose on the total, say $3000. take that divided by the total number of guests (say 300?) is $10 per guest. So you probably can look for hotels in the $110 range...
For me, i had a sunday lunch, so i know most people are probably giving $60. my lunch venue was $70 per person, I aimed for a max $3000 loss with the worst case scenario that average ang bow was $50, but most of our guests give $80 (though some gave $50) and we were abt to break-even even though we gave my mom abt 4 tables.
Do u have a wedding budget worksheet to help you calculate the expected and final amount of spending? because that would help alot for the banquet thingy, especially in earlier part of the wedding planning.