i kamj,
oh dear, you're in a difficult bind, made worse because of your and husband's feelings about this. i'd say you need to deal with it sooner rather than later, because it's upsetting you. and the more upset you become, the harder it will be.
technically you've been asked but your sons haven't. so technically you do know the answer. but if you think it's possible they've been omitted from the invitation accidentally, you need know. i'd think easier for bride's father to ask her, because it'll be easier for her to tell him "no" than you. but if he's going to put it off, or try to coerce her, then you're probably best to ask her yourself. perhaps open the discussion with questions about the wedding, show your interest in her big day. maybe talk about what you think you might wear? then, as lightly as you possibly can, ask if you've understood correctly that the invitation is for both you and hubby/her father (however you usually refer to him). that way you're not mentioning the boys, but allowing her to say "and the boys". (or not, as the case may be).
i don't think anyone should be upset about the bride and groom's decisions. but when you know who's invited you can decide on your response. you will not be seated on your own, but on a table of potential new friends.
if you want to maximise your relationship with DH's daughter, then go joyously.
if you can't make reasonable arrangements for your sons, then decline politely.
i wish you well, but please don't be upset whichever the answer is. she won't be not inviting them because she doesn't care, but because she doesn't have enough seats for everyone she wants to invite.
x