Taking into account your plan, I would propose to cross Pyrenees from Arudy or Asson, following the valley up to Laruns. From there you have to leave the Pic du Midi just to your left, and direct to the Canfranc valley. You will leave Pyrenees in the vertical of Jaca, very near of LECI for a short (or maybe long) break before continuing to Marugan.
I have made this crossing several times with a Tecnam P2002 and with good weather is 'easy' and the views are really stunning!.
(Look at
this gallery if you want, it contains several photos of this crossing)
I recommend to do it in the morning, as soon as possible and not later than noon or early afternoon. In summer it is very likely to found big CB formed over Pyrenees.
Once in Spain you won't have to cross anything like the Pyrenees in extension, but take into account that we have a lot of mountain ranges and almost all the country is between 2000' and 3000' AGL, even if it is flat. For example, Marugan is at 3000'.
For the base in France from where to do the Pyrenees crossing, I would recommend
Montpezat airfield. An ULM-only grass field with lodging, free wifi, unleaded mogas and very helpful people. Maybe it is a bit far from Pyrenees, but if you take off early in the morning it is ok. If you prefer something closer to Pyrenees you can expend the night in Auch/Lamothe (LFDH). Very big asphalt runway with a decent sized town very near. Take into account that this is a french-only AFIS airfield.