we went on honeymoon with a 5 month old, it was hard in some ways, but still a good time to go. We got a static caravan in the south of France, lovely place to go though a bit hot for me. Personally I have now given up on flying completely and woudl thoroughly recommend a UK self-catering holiday. but -
Things to consider:
if flying, take own carseat - car hire companies don't always have them and the ones they have don't always look very good.
our ds learned to roll over while we were away. therefore you will need a travel cot or at least a portable cot side (these are a lot lighter) for a single bed.
Stick at breastfeeding if you possibly can - bottlefeeding is a pain while travelling, though doable. We took sterilising tablets and I spent a lot of holiday time fiddling with bottles.
If your dp is not tremendously hands-on during the first 4 months (I'm assuming that they will be, of course) the holiday could be a shock, but quite a salutary one. It was the first time that my dp had quite cottoned on what hard work it was, as I was doing most of the nights and early mornings for the first few months (more fool me! but he was working full time plus on very sedating medication). Anyway, it was a good thing and he did more afterwards.
Heat is a bit of an issue with babies and it's a drag constantly fussing about suncream, hats etc unless you are staying in a nice shady house.
Consider just paying for more help at home for 2 weeks! temp nanny?