Hi N.,
I agree with you 100%. They need to stop doing this with her. She will only grow more and more needy, especially with you, and possibly bond even more with the grandparents because she gets what she wants from them. I've nannied for a while and I've been with a family that refused to put their baby down. He cried all day with me because I refused to hold him all day. Their older daughter was very spoiled, fussy, and needy, even at three. She could not do anything independantly.
It's true that grandparents spoil, and the rules change when the grandparents are around. I'm sure there are very few couples who don't have this problem. I know I have this problem with my parents, but they spoil in the way of brining gifts, skipping naps, and being lenient on meals, rules and what not. They don't live close though, so we only have to deal with that about once a month. Nothing compared to what you are dealing with.
I do believe that you have a great opportunity for your daughter to be with family rather than in daycare, or with a (let's face it) stranger, if they can't respect your wishes, then she is better off with strangers.
On that note, I have worked at a daycare myself, and I will NEVER enroll him in preschool. I'm a little bit biased because I had a bad experience, as a teacher at my daycare, but I would never do it, even with me in the next room. I would suggest a home daycare situation, or someone to come to your home. Just make sure you do your research on the person and get plenty of references. I have been through the process both for my son, and I am also a nanny myself, so I can help you out if you'd like. I've found some very good sites, and I know a few agencies you can contact.
Good luck with everything. Hopefully your husband is on your side, and can get through to his parents. If you ever need to talk feel free to contact me.
M.