There's a bleak old image of a divorced father treating his kids to a film on a grey afternoon before shepherding them to a burger bar for a treat before taking them back to their mother and heading home alone in the rain to a poky flat.
But, as they say, that was then, and this is now. Life has moved on, the courts offer separated fathers better contact with their children in almost every case, and there are plenty more options for fathers.
Much of the time you simply want to spend time with your children in a relaxed atmosphere, and nothing beats home for that. It might not be the home they knew, but take them to your place, whether it's a flat or a house. Give them a chance to feel comfortable there, to become used to your surroundings.
If you can, have things there they'll enjoy, like a game console, maybe even one they don't already own. Encourage them to treat the place like their own. It's much easier to talk in surroundings like these. If the place is big enough and you can have them overnight, let them stay, with a room to call their own, and remind them that they now have two homes, not just one, that they're always welcome - and mean it. Let them decorate the room and truly make it feel like theirs.
You can make evenings seem special and fun with a pizza and DVD night, as long as you allow them to choose the movie. Even if it's one you don't really want to watch, sit through it anyway, share the time fully with them.
Remember, the time together isn't just for you, it's for your kids, too. You want them to have fun, not feel it's a duty. So don't spend all your time at home. Do things, but make them special if you can (although going to a movie can also be a good time).
In the summer, pack a picnic and head out into the country. Take a hike, get some exercise, enjoy the views. You'll all feel better for the exercise and fresh air, and they may even develop a taste for walking and nature. There are almost certainly places to go within easy reach of where you live, or go farther afield, perhaps somewhere the kids have never gone before.
If there's an event they really want to attend, buy tickets and go with them (or, if they're older, drop them off and pick them up). It can be a show or a concert, or almost anything. You could even try something different, such as a trip to a museum or a theatre.
Depending on relationships, you might be able to negotiate with your ex to have the children for a week or two during school holidays. Take them away with you. It doesn't have to be four-star fancy, just somewhere fun and different, whether within the UK or abroad (however, if you're taking them overseas, check to see what you'll need. Apart from passports for everyone, it might also involve a letter of permission from your ex).
A holiday together can be a magical time. You might not feel relaxed at the end of it if you've had to take charge of them for an extended period, but you'll still feel good from the time spent together.