I'm sorry to hear about your dads long illness. As so many of his friends supported him, you might want to mention that in your email. E.g.
" As you know, dad had been unwell for some years and the whole family /mum and I have appreciated the way his friends have supported him and us during this time. We hope you can join us to celebrate his long and happy life "
Etc etc
The pub sounds like a great idea, and yes it's often a happy and important part of the day as people share good memories. Make sure there's food as well as drink, especially if people are travelling.
I know it's very stressful to organise and attend, but a good funeral can really help everyone, it's an important step on the journey. And you will feel that you have done a good job of it, for his sake and for friends and family.
My tip is to make sure that whoever does the eulogy has written it all down and you have checked it. Make sure it's personal, complete, accurate and you like the tone and style.
And preferably use someone who has some experience of public speaking.
I've heard some shocking ones from experienced speakers ( vicar , very senior barrister ) and some wonderful ones ( vicar, family member ) that make me smile even now when I recall them .
If you decide to do it yourself, make sure you have a back up plan in case you are overwhelmed on the day and can't do it. Even if it's just the vicar /priest to read out what you were going to say. You will feel less anxious if you know there's a Plan B.
You want to include stories about the different parts of your dads life e.g. Bowling club, work. If you don't know any good anecdotes from these places , ask your dads friends who will be happy to share.
That way, your dads friends from these places will feel included in the service and that part of your dads life will be honoured.