There are a number of companies doing the Med. at that time of year; some good, some o.k. I have read lots of good reports about Celebrity and Costa but, as English is not the first language of the crew and the majority of their customers I would suggest they might not be ideal for your occasion. Princess get mixed reviews; they are the American arm of P&O and are crewed by yanks and prices are charged in dollars and I hear can be pretty expensive, especially as they add 15% to all bar tabs and tips are fixed and expensive. This leaves Cunard and P&O. They are both crewed by British sailors and, though the bar,cabin and restaurant staff tend to be either Indian or Phillipino they all speak perfect English and are as helpful and attentive as you could wish for. Cunard is more expensive and don't offer many Med cruises but you do get what you pay for. The only down side with them is that they still, in effect operate a 'class' system as your dining room is allocated according to how much you've paid for your cabin. So all of the people in the cheapest accommodation eat together etc. etc.
It is probably the most formal as well. So it all depends on how comfortable you are with all of that.
No doubt, in your circumstances they would really look after you well, and you never know you might even get an upgrade.
That's also a possibility on P&O. they are also more formal than most but not too much so. I took my wife and twin 21 yr old daughters on a two week trip around the Med. last July on board P&O's Oceana and we all agreed it was the best holiday we had ever been on.We met some lovely people and had a great time. There were three formal, black tie nights and the rest was a mix of either suit(or jacket and trousers) or casual, with the odd theme night thrown in. Be sure to pack a Hawaian style outfit. I wasn't really looking forward to the formality but I must admit that I really enjoyed it and the ladies loved the opportunity to dress up. In the main the rest of the passengers were just ordinary people out to enjoy themselves with barely a 'stuffed shirt' in sight and definitely no drunken hooligans. There were kids on board but we hardly saw or heard them because there is so much for them to do and it is so well organised. Some cruises are adult only which rules out the risk of any rowdy kids but we never saw any.
As for the food, we've never quite got used to being back on dry land because nothing we've eaten since has compared. Apart from the odd dish which was not prepared to my liking I thought everything was perfect. The staff quickly get to know your preferences and really do take care of you and I know they lay on things especially for people who have a reason to celebrate.
The price of drinks was pretty much what you would pay in an average pub and there was nothing extra added on to the bill. Tipping is taken automatically unless you tell the reception staff from the outset that you wish to tip personally. The staff prefer it this way as, otherwise they end up sharing there tips with the Maitre D (who isn't the one doing the work) and others who may have contributed nothing to your holiday. Everyone's got their own opinions on the subject but I prefer to give to whomever I believe has helped to make my holiday enjoyable. Tip your cabin steward, depending on how helpful or otherwise he has been and your regular waiters whom not only depend on the tips to survive but whom you will soon see deserve every penny of it. The bar waiters don't normally get tipped as they have a bonus incentive scheme which helps boost their income but we had one that was so good to us that we had to give him a tip. My wife almost took him home with us.
I hope I have been of some help to you. I'm sure you will have a great time and if you need to know anything else just ask away.