She's not making any time for you. It's just common courtesy to make someone else a cuppa when you make one for yourself or to make enough dinner for you to reheat when you get in, not expect you to make your own. She's clearly trying to tell you something with her behaviour but if she won't open up and actually talk about it in words, what can you do with that?! Its no wonder you're frustrated.
It sounds like she's stuck in a rut, tired of her life, but she probably feels guilty being resentful of the DCs so she saves it for you. Its not fair.
my wife insists on getting into bed with the girls eveynight and always falls asleep with them She has replaced you with them in her affections and she needs to realise that this way divorce lies. You need to make each other a priority sometimes and you can't do that if she never comes downstairs to spend time with you.
However, if she's falling asleep when they do, she must be knackered. She could be depressed or just have no enthusiasm for doing anything after a busy day with the kids, but this isn't sustainable.
I'd be saying either something changes or you'll be leaving, as you deserve a full and loving relationship (that doesn't mean she OWES you sex on tap, it means that for a relationship to survive you DO owe each other the bare basics, a hug, a kiss, an evening watching TV together with a cup of tea you take it in turns to make each other!)
Is it possible that you've put pressure on her in the past if she shows you any affection that it has to lead elsewhere? That's often a reason why women switch off, they've learned that even a hug or a kiss is taken as foreplay so its 'safer' just to keep your distance. I'm not saying that IS the case, but its a possibility if that has happened previously.
I know when kids come onto the scene everything changes and often the mum feels 'touched out' after a day of kids climbing all over her, but you both have to be happy with the new normal, and you're clearly not. If she is, then she can't see why she needs to change anything, but she needs to listen to your feelings. If she won't talk and won't go to a counsellor, there's not much you can do to fix things on your own. You don't have to live like that.