You can do whatever you like @Millionairesshortbreadshort and despite all the 'you must be honest' and 'it's deceitful' and 'unhealthy and odd' and your marriage must be shit - or will go downhill fast' type comments, many people do things without their spouse knowing. Sometimes because they know they will kick off or moan, and sometimes because they know they will want to join them/join in. (And they don't want them to.)
I have done things without DH's knowledge, nothing bad like seeing other men or racking up 1000s of £££ of debt without him knowing, but just like you, booking holiday leave for myself, popping to maccie d's for an ice cream and a coffee, and buying a box of chocolates to munch on when he's gone to work on a night shift.
Not that he will be mad/pissed off/angry, but just like if I said I went to maccies, he would pull a face as he didn't get to have one, and he would have whinged if he knew I had the house to myself for the day, and would have booked the time off too, 'so we can be together...' And the chocolates I open when he's off to work because I don't want to share them with him ... I share most stuff, but want a certain thing to myself. That's my right, but he would scoff two thirds of them.
He needs to be with someone a lot more than I do, and I am happy without him here for HOURS, several days even. I am happy WITH him here, but do enjoy time without him too. He doesn't enjoy time without me, and always wants to do stuff together, so sometimes (not always) I make excuses/tell white lies to be on my own too.
Not a crime, and we are still going strong after nearly 40 years together (35 married!) He does things I don't know about too. I have caught him out a few times, but not let him know I found out. Just trivial stuff, but I still found out. Didn't go snooping but I did find out.
And as I say, most people do stuff their spouse doesn't know about - yes they really do! They don't need to know EVERYTHING.
Book your leave and don't tell him. Enjoy your time to yourself! 
Ignore the smuggy sneery judgy feckers!