To go on holiday, instead of to a wedding

[Figuringitout]

I feel very conflicted.
DH and I have had a really shit year and could do with some quality time together. Some friends will be in Cornwall over Easter, which also happens to be our wedding anniversary, and have invited us to join them. Our Dd gets on well with their Ds and we haven't seen them for ages so we agreed to go. They have booked, and were going to regardless of whether we come, but we've not booked anything yet.
We had just made these plans when we got a wedding invite - for the same weekend. We'd seen the friends socially, and knew the date, plus we'd received a 'save the date' card, but I had completely forgotten about the wedding. These are good friends and ordinarily I would have loved to go as some other old friends will be there. Dd is not invited, which normally would be a good excuse to get some drinking in with DH, but I am pregnant so can't do that.
AIBU to miss the wedding, which I know will upset my friend, to accept a more recent invite to go away.
P.S if we do go, how on earth shall I word it when letting her down??

Do whichever you want to do.
I had an invite to a wedding, which then turned out to be just for the evening do. Which was then put forward a week and a day meaning that instead of being on a saturday when both myself and partner would be off work the next day, it was a Sunday. I didn't go to it as the chance to go on holiday arose and even though I could have gone on holiday at a later date, going the day before the wedding made it cheaper.
The bride had already ordered the food but understood.

Max Save the dates should mean an invote. Incredibly rude to send a save the date and not send an invite.

Just called my friend; am now definitely going to the wedding. I know we'll have a good time, just wish I was a bit harder to guilt trip.
Thanks for all the advice!

Hooray. You are doing the right thing op. I'm v pleased my RL friends aren't like the posters on this thread tbh.

Totally the right thing to do. Weekends away can happen anytime, good friend's only marry once or er twice, three times max.

If ever I'm invited to a wedding I assume it's because the people getting married really would like me to be there, not just to make up numbers. Anyone who says you'd not have been missed is wrong imo. Have a great time.