Rather than offering a draw individually in each game, which is of course possible but allows the opponent to accept one and reject the other, I guess you mean a "package deal" of two draws which, if rejected, means both games play on. As far as I know you can only do that by asking your opponent in the chat, and your opponent has no compulsion to co-operate if they don't want to.
The ethics? I've seen it done before. I would place it in the "grey area". Personally I wouldn't recommend trying it under any circumstances.
Is it possible to offer a draw for both games in a two game match? Is it allowed and considered ethical?