I think you teaching her how to spend/save is very important, if the ecomony has taught us anything lately, it is that people spend too much and don't know how to save. Letting her spend every cent she recieves will eventually lead to the attitude of spending without consequences and she will end up in debt. I know this sounds silly now because she is only 7, but it is what we learn in the formative years that shape our lives.
If you and your husband can't agree on a strategy, maybe you could suggest to grandpa to please put his money in a savings account or a college account for her (and maybe buy her something small with some guidance from you in her likes and dislikes). That way he is still giving her something and it won't disappear and will be something she will really need later in life. I know it isn't teaching her how to handle money but you can find other ways to do that, and hopefully, there will be no disagreeing involved.
You are doing an excellent job, keep it up!
J.