confirm again by phone to all invitees 1-2 days before the wedding dinner. you then know the exactly no of people to come and arrange the tables again. When you arrive the restaurant you say how many tables you need actually. Even if you ordered a lbit more - they should not charge the excess table. But this point you should confirm with the restaurant when you make the deposit.
Some areas cannot add more tables because of insufficient space.
Usually bridal family should quote the no of tables they want in the wedding dinner - then the gift cheques of these tables all go to the bridal family.
Then base on this '"cost", bridal family can ask the groom to quote the gift money to the bridal family - because the gift money will actually depend on the no of table (cost) he has to pay for.
Each side should have a budget in mind first.
Some family don't need the wedding dinner just want to receive full amount in gift cheque. That's why sometimes the wedding dinner is hosted by the groom family only.