Gloucester for lunch?

Good Vietnamese place on Southgate St. opposite McDonalds.

But generally, no.

Slam 69 bicycle shop is worth a visit to ogle at their vintage MTB's and their vast array of stock.

I’d head to the docks. A good few, non chain, options there and a good selection of beers if that’s on the cards.

Gloucester town, generally no but, Hooker and Eight on Westgate Street is excellent pizza.

Smaller bites I’d go Hungry Bean Cafe near the rugby ground.

Failing that ….. Gloucester services if you don’t fancy heading into town.

There’s a Thai place near to ‘spoons. Area doesn’t look impressive but the food is pretty good.

Or Cheltenham isn’t too far of a diversion and The 131 does a nice lunch.

Caffe Corretto in the docks is very good, most of the other eateries there are a bit expensive.

Go near the docks, easy parking at the shopping centre. few chains about, my kids like Bills! Have a look round the Cathedral and see which bits you recognise from Harry Potter films.

Thanks all. Looks like I'll be suggesting the docks to MrsG.

Cheltenham has better restaurants, but you have little kids so a chain place will be fine. Gloucester's got some really interesting history if you can dig it out amongst the grot spots.
For a couple of hours stop, I'd park at Hare Lane, walk past the cathedral (maybe a quick peak inside - Harry Potter bits), then onto the docks and find your preferred chain restaurant.

There's a pub in Longford, the Queens Head, that does great pub food, on the outskirts of Gloucester, two mins off the A40.

https://queensheadlongford.co.uk/

Or, slightly but not that further out, there's the Red Lion in Wainlode that is in an absolutely beautiful spot on the river.

https://www.redlionwainlode.co.uk/

As others have said, Gloucester docks or quays for a choice of family restaurants, pick depending on budget and taste.