Can I do this?

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We will have at least 4, possibly 7 for our next trip. Can I make 2 reservations at the same restaurant. Ex: 1 ADR for 4 and 1 more ADR for 4 at whatever restaurant for whatever time. Instead of making 1 ADR for 7people. That way if it just ends up being the 4 of us, I will just cancel one of the tables. Is this allowed? The reason I asked, is because two years ago, at the last minute, my sister, cancelled eating with us 3 nights, due to finances, luckily, we were able to keep everything, but I was stressing out because I was going from 10 to 6.