I totally agree with those saying you go and husband stays home while you order something reasonable (and don't cave to pressure to buy "Just one drink" or whatever).
One thing to add, though. If your family is a crowd that expects every spouse to be at every event every time, and they're going to carp at you or tease or otherwise make it A Big Deal that husband isn't there -- well, still go without him but be prepared for this, and have in your mind some polite but firm lines to shut down any commentary on his absence. "Oh, he and Son are having a guys' night in." "He's got a lot going on at work right now, so I suggested he slow down and have an evening with Son. He sends his regards." Whatever works. Immediately after any such comments from you, change the topic that instant--"So, how is Your Kid? Didn't she have a basketball game coming up?" and so on. Be prepared before you go and you can fend off any comments on husband's absence.
If they make it all about "Oh, you couldn't afford to both come, gosh, we're so sorry," don't put up with that condescending talk. Just smile and say, "I'm here for Sibling's big night out and isn't this food great?"
It really is time to start doing these events on your own terms--as you noted yourself, you're an adult and yet they still lay on the guilt. Go on your own, smile and be very sweet while being very firm, and always, always turn to another topic immediately -- they will be distracted if you ask them about themselves, their kids, etc. If they still guilt you after the fact about how "Husband didn't come, we're really missed him" and especially if they refer to your finances -- next time, be too busy and have another event on the day of some affair that you can't afford.
Maybe plan some of these events yourself in a simpler way from time to time so it's not always about expensive restaurant meals, if that's how your family tends to roll. Keep it smaller, have a birthday sibling over to your home for a meal instead (without lots of other people there), etc.