Totally normal reaction OP, it in no way diminishes how strong you are and have been, you have to allow yourself this grieving process (it's very important, and IT WILL pass, but does take time).
I did the 'compare'- ended up losing way too much weight and dont even get me started on what happened on Social media!!.. (I was so pleased when you mentioned you were coming off FB etc, honestly for anyone going through a breakup 'delete, recover, pick your friends if you decide to go back'...there should be rules around relationship breaks on SM! so destructive).
Your holiday would have been now, of course your feeling the 'we would have been....', but remember if you didnt find that iPad you would have now been on that holiday with a cheating dick still playing his game....which would you have preferred?
You'll always hold the higher ground OP, how you left was so impressive, it took immense courage...now allow yourself some time to come down from that, keep your friends and family close, perhaps get really involved in some mums clubs with your LO, but one foot infront of the other for now is totally good enough 