THE boys want to keep going to Pluto to make sure it's there.
Pluto is a dwarf planet they say, not a proper member of the solar system so if we are going to do space travel properly we should check on the far-flung little guy.
Let me explain.
We are on a family cycling holiday based in York and are exploring a cracking ride along the Trans-Pennine trail which has turned a disused section of the old east coast main rail line into a scale model of the solar system.
It starts at a huge golden model of the sun and has miniatures of the other planets along the way in distance proportionate to that in space.
So while Mercury, Venus, Earth and Mars pass quickly, the outer planets come a little more slowly. Still, that gives us the chance to take in the beautiful countryside and enjoy the traffic-free riding.
Our hosts for this adventure are Scoot, a local firm who have made it their business to bring cycling holidays to Yorkshire.
And they are doing a top job, organising everything so all we had to do was provide pedal power and a sense of adventure.
As our train pulled into York Station, Scoot's Cai and Sally met us with the new bikes that were to be ours for the next three days.
After a welcome and bike fitting, plus a talk about the kit which included helmets, pannier bags and puncture repair gear, the girls took our bags to our accommodation and we got on our bikes.
Scoot had sent us a map pack earlier so we already had a good idea of longer trips we would tackle but for starters we were content to get our bearings with a riverside ride along the Ouse before heading back into town to check out our digs.
By the time we got to the well-appointed National Trust flat in Goodramgate next to York's famous Minster our bags and a welcome tray laid out with the makings of a well-earned cup of tea were waiting for us.
The Tour de France has its Grand Depart in Yorkshire next year, but Scoot is already doing its bit to put the northern English county on the cycling map.
It offers self-guided tours for cyclists of all types and families with kids of different abilities.
York has so much to see and do that we split our days, cycling in the mornings and then taking in attractions in the afternoons.
We used a York Pass card which worked out a huge saving on paying individual entry fees to attractions and, after three days, we had only scratched the surface of what the area has to offer.
So as we handed the bikes back at the station and grabbed our bags which had been transported there for us, we staged our own Grand Depart and vowed to be back.
The Shields family visited York with Scoot Cycling Holidays who offer four-night self-catering holidays based in the centre of York, including bike hire for £795 for five people. www.scootcyclingholidays.co.uk for full information. Details of the York Passes at www.visityork.org