The first thing you have to do is take this outside of the bedroom.
The second is to stop think that you can do anything about the situation without talking about it ("she will see what I really want without saying it ") - not going to happen (don't hesitate to correct me if I have misunderstood

). It is absolutely primordial that you communicate about this - communication is one of the cornerstones to a good relationship.
It seems to me that your main issue is with the 3yo in the bed with you. So you need to say so. Do it (as said above) outside of the bedroom. Choose a moment when you and your wife are alone and unlikely to be interrupted. Tell her that you miss her, that you miss having her all to yourself. Tell her that you understand that your children need her but so do you. She is now a wife and mother but that doesn't mean she has to stop being a lover. Offer to take care of the children for an hour when you get home in the evening (I'm assuming your wife is a SAHM?) so that she can have some "me time" (trust me, this works wonders - I speak from experience - all time spent like this will be rewarded a hundred times over

). The other added advantage is that you get to spend quality time with your children and in the years ahead you will be glad you did.
When did you last have a date night? You are going to need to plan for one regularly. It takes time and patience to fuel the romance in your couple and you can't do it if you don't have time to (or won't make the time to). Find yourself a sitter. Do you have any family nearby? Good trusted friends? You need to get out for the evening and away from all the every day stuff.
Did I understand that your 3yo goes to bed at 11pm? If so, it's time to point out that this is very late for a child and that you're not doing her a favour (imagine how difficult things will be when she gets to school?). It's time to get her on a more suitable schedule (bed at 8pm or earlier) and it would be a good idea to get her to start using her own bed. It will get harder and harder to get her out of your bed as she gets older. Tell your daughter it's time she was a big girl so she can set an example to her baby sister. Then you work on a routine (together) for getting her to sleep in her room - bath, story, etc.
Well, this turned out to be much longer than I intended - I sure hope that some of it will be of help to you. I truly understand that you want things to change but that you don't want to upset the applecart either. Not an easy situation. However, it comes down to two things:
- communication
- preservation of your couple.
I wish you all the best in this.
There's nothing inherently dirty about sex, but if you try real hard and use your imagination you can overcome that.